Home » Electrical Wiring Directory » Fluorescent » 77 Comments

Fluorescent Lighting Problems and How To Fix Them


By Dave Rongey - Summary:

How to Fix Your Fluorescent Lighting Problems: The Most Common Problems with Fluorescent Lighting and How to Fix Them.


Guide to Fluorescent Light Fixtures and How to Fix Them

Electrical Question: My Fluorescent kitchen light was not coming on quickly if at all.

  • I replaced the ballast which fixed the problem for about 3 days.
  • Now it’s back to not turning on.
  • When you hit the switch you see a flicker of light at one end of the U shaped bulbs but that is about it.
  • This light has 2 U shaped fluorescent lights.

Appreciate your help !
Background: Jim, a Homeowner from Southington, Connecticut.
See more about Home Wiring for Connecticut

Additional Comments: Great website.

Dave the Electrician’s Reply:
Thanks for your electrical wiring question Jim.

How to Fix Your Fluorescent Lighting Problems

Application: Fluorescent Light Fixture Wiring.
Skill Level: Beginner to Intermediate.
Tools Required: Basic Hand Tools and Safe Ladder.
Estimated Time: Depends on personal experience, the light fixture and access to the light fixture.
Precaution: Identify the light fixture circuit, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Replacement parts for the light fixture should be compatible with the type of fluorescent lamps that have been installed.

The Most Common Problems with Fluorescent Lighting and How to Fix Them

  • Bad Lamps
    • Indicated by dark circles at the end of the lamps.
    • Simply replace the lamps, typically every two years depending on the amount of use.
    • If you allow the lamps to burn out in the sockets this can burn out the ballast.
    • When you replace a ballast always replace the lamps.
    • Lamps are much less expensive that a ballast, so don’t ignore this.
  • A Bad Ballast
    • As indicated above, if replacing a ballast make sure it is intended for the exact lamps that are being used.
    • If the fixture had an older magnetic ballast then you may consider upgrading the fixture ballast to a solid state ballast.
    • In most cases the sockets will not require changing, but again, you will need to match the lamps to the ballast.
    • Solid state ballasts are much more energy efficient, produce less heat and are less sensitive to cool temperature starting problems.
  • Single Pinned Lamps
    • This is where one of the lamp pins is not in the socket or not making contact in the socket.
    • This is a very common problem, but is easily fixed.
    • Remove the lamp and reinstall it paying attention to lining up the pins with the lamp socket and then giving the lamp a twist to seat the pins into place.
    • Some sockets are made to push the lamp pins directly into place with a little snap-in pressure.
    • Examine the lamp sockets to see which type your fixture has. Never force a lamp.
  • No Ground Wire
    • Fluorescent lights require a ground wire from the electrical circuit to be attached to the metal frame of the light fixture.
    • In some cases where the ground wire has not been attached, the fluorescent lamps may not light up all the way which will cause the lamps to burn out prematurely.
  • Cold Temperatures
    • Many of the older magnetic types of ballasts are slower to start in colder temperatures and after they do start the lamps flicker until they warm up.
    • Upgrading the light fixture to an electronic ballast and new matching lamps usually takes care of this problem.

More about Home Lighting

How to Install Kitchen Electrical Wiring
kitchen-electrical-wiring

Kitchen Electrical Wiring

Fully Explained Photos and Wiring Diagrams for Kitchen Electrical Wiring with Code Requirements for most new or remodel projects.

Using Testers to Identify Electrical Problems
digital-tester

Testers to Help Solve Electrical Problems

Troubleshooting Electrical Wiring
Types of Electrical Testers

Circuit Breakers for Light Fixture Circuits

Electrical Codes for Lighting Fixtures




Learn How to Wire it Right with my
Complete Guide to Home Electrical Wiring
Perfect for Homeowners, Students,
Handyman, Handywomen, and Electricians
Includes:
Wiring GFCI Outlets
Wiring Home Electrical Circuits
120 Volt and 240 Volt Outlet Circuits
Wiring 3-Wire and 4-Wire Electric Range
Wiring 3-Wire and 4-Wire Dryer Cord and Dryer Outlet
Troubleshooting and Repair Electrical Wiring
Wiring Methods for Upgrading Electrical Wiring
Electrical Codes for Home Electrical Wiring
....and much more.

» Click here to learn more about Home Electrical Wiring «
  repair electrical wiring  


Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all projects.
« Incorrect Repairs That Create Home Electrical Hazards How to Activate a Garage Light from the Garage Door Opener »

FAQs Frequently Asked Questions and Comments

77 Responses to “Fluorescent Lighting Problems and How To Fix Them”
  1. Doug says:

    Thanks for your great service on this site! I’m replacing the ballast on an 8′ single bulb fixture from T12 to T8. The fixture has 1 blue wire at one end and 2 white wires at the other end. Ballast has 2 blue and 1 red. How do I connect them? Thanks!

    • Dave Rongey says:

      Hi Doug,
      Make sure you have the correct ballast to match the circuit voltage and the lamp of the light fixture. Please refer to the wiring diagram that is included on the new ballast, and transfer the new wiring as described. Keep in mind that when connecting the wires from the ballast to the lamp sockets the wire colors of the original fixture sockets do not matter as long as you are following the wiring diagram, however the circuit wire colors do matter and should conform the same as the original ballast.
      I hope this helps,
      Dave

  2. Landon says:

    I changed my old 4 lamp t12 to a new 2 lamp t8 fixture. It worked great for a few days, but now it won’t turn on. I changed the wall switch and it came back on for a few minutes, then cut back off. Could it have anything to do with too much power sent to the smaller fixture, or is it more likely a bad ballast?

    • Dave Rongey says:

      Hi Landon,
      The electrical circuit power should not be an issue. I would go through the checklist as outlined above, and be sure the pins of the lamps are making full contact with the sockets. If the sockets become arced this can cause a bad connection which is enough to cause intermittent lamp performance and erratic light fixture starts.
      I hope this helps,
      Dave

  3. David says:

    I recently replaced a 8″ circline 22 Watt bulb. New bulb will not come on. I checked power at the plug from the ballast. I have 120 volts so ballast is good. I tried a few different bulbs to make sure it was not an issue with bulbs. Do you have any thoughts on this problem? I don’t know what else to check. Thanks.

    • Dave Rongey says:

      Hi David,
      If the previous Circline lamp burnt out while still in the socket then most likely the ballast will need to be replaced. Even though the socket of the ballast appears to have 120 volts the ballast may still be bad. Also, make sure the socket connector is configured properly where it plugs into the lamp. Some of these types of socket plugs can be tricky to connect.
      Replacement ballast can be a little pricey, you may want to consider replacing the light fixture with a new round LED fixture which will be much more energy efficient.
      I hope this helps,
      Dave

  4. Bobby says:

    I have a row of old T12 8′ light fixtures. I replaced the ballast in one of the fixtures (SM-2E75-S-1-TP) with the replacement B260IUNVHP ballast. It has a extra blue wire so I wired the two together and it worked for about 2 hours and then it went out again. What am I doing wrong?

    • Dave Rongey says:

      Hi Bobby,
      Double check the wiring diagram on the ballast compared to how you have the wiring connected in the light fixture. You will notice that the wiring diagram for this ballast shows that there is one blue wire for each lamp socket at one end of the light fixture, and if there is only one lamp in the fixture then the extra blue wire should be capped off. The single red wire of the ballast is connected to the lamp socket(s) at the opposite end of the light fixture, and shared if there are two lamps.
      I hope the helps,
      Dave

  5. Jim says:

    I have five 8 bulb T5 light fixtures. They all seem to have the same problem of dim light output. All of the fixtures are less than 2 years old. I checked everything you suggested. Is it possible for a ballast to read good but still make the bulb produce dim lighting?

    • Dave Rongey says:

      Hi Jim,
      Sorry to hear about the dim light problem with all of your fluorescent fixtures. Note the brand of the lamps and contact a representative to see how many hours the lamps should be warranted for and then compare that to the number of hours the lamps have been used. A quality brand name standard T5 fluorescent lamp is rated up to 30,000 hours of life based on 12 hours of usage after a single start. Keep in mind that all lamps are not the same, and an off brand lamp of lesser quality may have a lower life span, and the same goes for the ballasts.
      I hope this helps brighten up you day,
      Dave

  6. Warren Buck says:

    I just put in two new t8 8ft fixtures and when turned on they are bright. After a minute or so, they dim in the middle of the lamps. Both fixtures do the same thing.

    • Dave Rongey says:

      Hi Warren,
      Double check the items mentioned in this post, especially the wiring and make sure the lamps are in the sockets properly.
      If the problem persists then contact the supplier of the light fixtures and explain the problem. Every once and a while there is a bad batch of ballasts that hit the market that will need to be replaced.
      I hope this helps,
      Dave

  7. flavio says:

    I have a row of fluorescent lights on the canopy awning at my shop, six fixtures in a row. Several have gone out yet the middle one still works. On the ceramic where the bulb hooks in it is burned. The other fixtures are not burnt so I took ballast from burned one and placed in one I thought ballast had burned out and still it will not work. What are the odds of five ballasts burning out at the same time?

    • Dave Rongey says:

      Hi Flavio,
      The odds of several fixture ballasts burning out at the same time are pretty slim. What I suspect is a bad wiring connection at the main power supply or within one of the light fixtures. The main power source should be located and the wiring connections inspected. The power to each light fixture ballast could be tested as well. If the tester voltage readings are not normal then trace the wiring of the power circuit back until the faulty connection or splice is discovered. The power should not be looped through the sockets of the light fixtures because a burnt socket would cause the loss of the circuit power to the rest of the light fixtures. If this condition is discovered then the burnt socket should be replaced and the wiring method corrected to prevent the circuit from feeding through the socket by using a pigtail splice with one lead wire connected to the socket.
      I hope this helps,
      Dave

  8. Steve says:

    Just installed a new ballest on a 4 foot t-8 florescent light with a motion sensor. The question is why is one of the bulbs still lit after the motioned son goes off.

    • Dave Rongey says:

      Hi Steve,
      Motion detectors work best with light fixtures that have incandescent or halogen type lamps, especially if the neutral wire of the motion detector is wired through the lamps. One way to eliminate the problem of dim or flickering fluorescent lights that are controlled by a motion detector is to have the motion detector trigger a small 120 volt control relay, and have the light fixture controlled through the contacts of the control relay, not the motion detector. The control relay should be carefully sized to stay within the voltage and watt specs of the motion detector, and have contacts that are rated for the volt and watt specs of the light fixture.
      Dave

  9. Laura Blohm says:

    Hello Dave! Love your site – we’ve read through most of the ballast issues and other responders questions but I have a kitchen light that is responding to the same issues. It is a 4 bulb, 2 ballast system. For awhile the two inner bulbs would not work, even after a replacement install. Then the outer about a week later. Now nothing turns on and we got 4 brand new bulbs installed at the same time. So after purchasing 8 new bulbs with no luck we turned to your site. We read up on the ballast and socket issues and one of the outer sockets is broken – it makes contact with the bulb but one of the little swinging arms on the inside that hold the bulb in place after twisting is missing? Could all this be just from the single socket? Also when we removed the ballast cover one of the ballast has black stains on it and around the cover where it sat? Is it OK to replace only one ballast?

    • Dave Rongey says:

      Hi Laura,
      Yes, a broken lamp socket will contribute to the problem of lamps not starting up. Your description of the black stains on the ballast and ballast cover is an indication that the ballast does need to be replaced, and yes – replacing only one ballast is fine, just make sure to get the same type of ballast and follow the same wiring pattern, or connect the wires as described on the new ballast wiring diagram. If a different type of ballast is installed, such as an electronic ballasts, make sure to have compatible lamps as noted on the label of the new ballast.
      Enjoy Your Light Fixture!
      Dave

      • Laura Blohm says:

        Thank you Dave,
        We replaced both of the sockets, as the package instructed, as well as both ballast. The middle lights turned on, but the outer lights still wont turn on. It stayed on for 3 hours then again they flickered and now none work. We even installed another 4 new bulbs. Suggestions?

        • Dave Rongey says:

          Hi Laura,
          I would first double check all the wiring connections, especially for the outer pair of lamps.
          Next, I would verify the incoming circuit voltage and test the integrity of the ground wire. In some cases a ground wire may be present but has not been connected to the ground wire of the circuit or bonded to the grounded system of the home.
          After that I would check to make sure and controlling switch or switches are tested and functioning properly, and that the switches are compatible with the light fixtures. Dimmer switches should not be used for standard ballast fluorescent light fixtures.
          I hope this helps,
          Dave

  10. Dave Edwards says:

    I have a 2 lamp fixture in an unheated garage. I converted from T12 to T8. I replaced the old ballast with the new electronic Ballast and all 4 sockets. When I turn it on the light is very, very dim. Do I just need to give it time to warm up?
    Thanks,
    Dave

    • Dave Rongey says:

      Hi Dave,
      Be sure to double check the wiring from the ballast to the sockets, and make sure both pins of the lamps are inside the sockets.
      Also review the items mentioned in the article above for other possible factors.
      I hope this helps,
      Dave

  11. Judy says:

    I have a two lamp 48″ Fluorescent light in my garage. One light went out, I replaced it with a new bulb, but in doesn’t come on. I switched the bulbs and the light comes on the one side but not the other. I have checked and the lamps are securely in. When I removed the other bulb, the one that wouldn’t come on, had a faint light to it. When I put the bulb back on the other side, it went completely out again. Any ideas?

    • Dave Rongey says:

      Hi Judy,
      I would suspect that the ballast has gone bad and needs to be replaced. After replacing the ballast be sure that both lamps are new to ensure best performance of the fluorescent light fixture.
      I hope this helps,
      Dave

  12. Steve Do says:

    I have single pin F96T12 lights, two per unit. I replaced the magnetic ballasts with new electronic ballasts in two sets. I wired them as shown in the diagram which was different from the existing setup. Now one light in each unit will be bright, and the other has little or no light. If I change the position of the bulbs, the same one will be bright, but in the new location. I started with 2 new bulbs, and switched them out with another two new bulbs, and the same thing happens. What could I have done wrong? Both units are doing the same thing.

    • Dave Rongey says:

      Hi Steve,
      Make sure that the F96T12 lamps are compatible with the new electronic ballast that you have installed, and double check the wiring connections, especially from the ballast to the lamp sockets. The label on the electronic ballast will state which lamps are compatible.
      I hope this helps,
      Dave

  13. Eric Burkland says:

    I have a T12 HO High Output light fixture with two lamps, and when I flip the switch on the lamps are very slow starting.

    • Dave Rongey says:

      Hi Eric,
      The performance of the High Output or T12 HO Light fixture lamps will be affected by all of the factors as listed in this article about Fluorescent Lighting Problems, especially if the lamps are old and need to be replaced, or if there is a lamp socket that has a bad connection which will cause the socket to deteriorate and require replacing. Because of the high levels of light that HO lamps produce they use more electrical current, therefore the sockets have a tendency to go bad over time, especially if the spring loaded socket becomes worn out, so be sure to check the lamp sockets.
      I hope this helps,
      Dave

  14. Paul Anderson says:

    Hello,

    I tried to add a pull switch to a 4′ shop light. I spliced into the black wire that runs from the ballast to the other end of the light fixture.

    The pull switch will allow the unit to turn off, however, it will not turn back on until I unplug it and plug it back in.

    It appeared that the power cord was molded directly into the ballast.

    How can I make the switch function properly?

    Thanks!
    Paul

    • Dave Rongey says:

      Hi Paul,
      A pull chain switch for a shop light consists basically of two wires:
      One wire connects to the incoming 120 volt power source.
      The other wire connects to the wire that leads back to the 120 volt lead of light fixture ballast.

      If the pull chain switch wiring is correct and the fluorescent lights do not work then check all of the wiring connections, and the circuit ground wire connection to the metal frame of the light fixture.
      Dave

  15. John Tanberg says:

    I just purchased and installed a HO-T5 2 lamp fixture in my shop. When turned on one bulb will light and the other bulb will flash 2 times and then both bulbs will turn off!!! Switching the lamp off and then on again produces a repeat of the 2 flash and off symptom. Any ideas?

    • Dave Rongey says:

      Hi John,
      Go through the items described above, and also make sure to check the wires leading to the sockets, that there are no loose wires. Every once and a while we can get a bad lamp or defective ballast.
      I hope this helps,
      Dave

  16. Dan M says:

    A T12 fixture was firing new bulbs dim. The other identical fixture fires the bulbs just fine. I replaced the ballast with an electronic one. It was the right one for the (2)F40T12 fixture. The bulbs are still firing dim and flickering, mostly at the ends, at first, then turning off. The housing has continuity with the ground wire with no readable resistance. NOTE: There is readable resistance, What I meant is the fixture is grounded
    My best guess is the new ballast is also bad.
    Thanks for any help!

    • Dave Rongey says:

      Hi Dan,
      Yes, you might have a bad ballast, however be sure to check the wiring between the ballast and the sockets. When converting from the old magnetic ballast to the new electronic ballast it is possible to mix up the wires. Also make sure the wires are inserted fulling into the lamp sockets, and that the pins of the lamps are fully inside the sockets. If one of the two pins is left out then this will cause the lamp to be dim and not fire up all the way to full bright.
      Dave

  17. John Laughli says:

    I have two florescent light fixtures in my kitchen. They are both 2 bulb and 4′ long. One has one switch to operate it. The other has two switches. The problem is that when I switch one on, it will not always come on. I may have to toggle the switch several times to get the fixture to turn on. When it comes on, it stays on and does not blink or anything. It works just fine. This problem is with both fixtures and all the switches. I am confused. They both worked properly for the last six years. Any advice would be greatly appreciated. Thank you in advance.

    • Dave Rongey says:

      Hi John,
      Factors that may be the cause of slow starting florescent lamps:
      The Lamps are starting to go bad: If the lamps are dark at the end then they need to be replaced, and it is best to replace the lamps in pairs. Typically lamps last anywhere from 2 to 4 years, depending on how many times they are switched on and off.
      Ungrounded light fixture: Is there a ground wire attached to the metal enclosure or frame of the light fixture, and is the ground wire really connected and bonded throughout the circuit? You can check this by using a voltage tester and making a voltage test from the power to the ground wire or enclosure of the light fixture. Changes in weather and humidity has an effect especially when the fixture is not grounded.
      Let the Light Shine On!
      Dave

  18. Duane Englund says:

    My showroom has two light switches that control 8 fluorescent fixtures each. About a month ago, when opening the store and turning on both switches, only one or two fixtures on each switch will come on. After leaving the switches on for a short period, I can flip the switch on and off rapidly and almost all of the lights will then come on. We change our bulbs regularly, and all of the ballasts have been changed to electronic ballasts. The bulbs and ballasts are matched. I had an electrician come to take a look, and after a brief discussion he said it is most likely the ballasts are bad and he would replace them and the bulbs for $75.00 each, 16 X $75.00 = $1200.00! I don’t want to put that much money into something that he said “most likely” is the problem. Any Ideas?

    Thanks, Duane E

    • Dave Rongey says:

      Hi Duane,
      The first thing I would check is to make sure the fixtures are well grounded.
      Next I would get information about the parts that were installed during the conversion, specifically the lamps and ballast, then see what kind of warranty there may be. Find out if there is a history of problems associated with the brands. It is always best to use good quality parts that have a great reputation and a company who will warranty the parts in an event such as this. I don’t know where you are located, however the estimate you were given which includes parts and labor is really not that bad, especially if the parts have a warranty.
      I hope this helps,
      Dave

  19. Frank says:

    We have closet light fixtures dating from 1991. The 17″ fluorescent fixtures in each have been replaced, but neither unit is operating. The housing does not appear to have access to the ballasts. There does not appear to be a way to dismantle the housing. A 20th century dinosaur? Would appreciate any input. Thank you.

    • Dave Rongey says:

      Hi Frank,
      Closet light fixtures are not always fun to work on because of the convoluted access, however my experience with similar fluorescent fixtures allowed me to have access to the ballast by removing the lens covering and the ballast was located in the center portion of the light fixture. Other manufacturers may have a cover plate over the ballast area. In any case, you may have to persist a little more, or your other option is to replace the light fixtures with new ones. This may be the best option if the new fixtures include the lamps. Buying a replacement ballast and the lamp may cost just as much as a new light fixture, compare the cost and see.
      I hope this helps.
      Dave

  20. Charles McCash says:

    I Bought 3 under cabinet lights from home depot for my workbench (2 4-ft, 1 2-ft). 2 of the 3 light fine, but the other (4-ft) fixture lights for 15 seconds or so then turns off. When the power is turned off, the bulb flashes briefly, then is off. At this point, the power can be turned back on and the bulb will light for another 15 seconds or so. Traded out the bulb; didn’t solve the problem. Checked the wires, all seems OK. Already exchanged one fixture which went out entirely after 3-4 uses and wouldn’t turn back on; the problem above is with the new fixture. All of the fixtures are new, along with the bulbs. Any thoughts? Ballast? Wondering if it was a bad day in the ballast factory and I got two fixtures from the same lot of ballasts…

    • Dave Rongey says:

      Hi Charles,
      I would check to make sure the circuit wiring is correct, making sure the power source is definitely 120 volts to match the light fixture required voltage. Next I would only connect to one light fixture all by itself and see how it does. If the circuit wiring is OK and the single fixture works then make your connections to the other light fixtures. Make sure you are not wiring the fixtures in series, but rather making the circuit connections color to color throughout each light fixture.
      Yes, there could be a problem with a batch of ballasts, but that is rather rare.
      Dave

      • Charles McCash says:

        Wired it up alone with the same result. Finally went back to Home Depot; they gave me another ballast (the 3rd). Problem solved. Thanks for your help!

  21. Betty says:

    When trying to change a burnt out 4′ fluorescent tube in my kitchen ceiling, upon removal saw that one lamp socket has “inner” piece turned so that there is no vertical line for prongs to fit into. (No pieces have broken off, just out of alignment.) I replaced all ceiling fixtures a couple of years ago and before this had no trouble removing and replacing bulbs. These lamp sockets are configured slightly differently. Because the “inside” of the lamp socket is twisted, does that mean it is broken and unrepairable, or can I coax the piece back into position?
    Thanks

    • Dave Rongey says:

      Hi Betty,
      The sockets for the fluorescent lamps can break to the point of either not allowing the lamp to be inserted or the pins of the lamp can not make contact, which will prevent the lamp from starting. If this happens the broken socket will need to be replaced. A replacement lamp socket can be found at most hardware stores or local wholesale electrical distributor. Make sure the replacement socket is the same size as the original.
      Dave

  22. nj says:

    Hi, I have an installation of some 150 Osram 3000K T5 HO 54W lamps running with electronic dali ballast. Somehow, they all run with different weird color temperatures. I would like to know what could be the reason for such anomaly and how to fix it. Thanks, NJ.

    • Dave Rongey says:

      Hi NJ,
      I have experienced a similar situation in a remotely located water plant where the power quality was not the best. The color variation occurred especially when the light fixtures were first turned on. If the power is a problem then a voltage conditioner may be helpful otherwise you may want to do some research on the brand of ballast and see if there are similar reports. Osram is a well known brand so I do not suspect a problem with the lamps. Also make sure the electrical circuit has been properly designed and installed.
      Dave

  23. Mike says:

    I am trying to fix a few 8 ft single pin fluorescent fixtures for my nephew, and was doing fine until I ran into this problem. The ends are the push type, where you push in one end and then the other end is fixed. I wired in the ballast – and then one bulb came on, the other didn’t. I checked and rechecked the ends – and it appeared they were fine. I had this happen on two fixtures – so I took the working ends from both fixtures and combined into one – and still the same result. I figured this meant a ballast -so I replaced the ballast with another one, and still the same. I know it is possible that both ballast are bad – but wondered if there were any suggestions. My basic question is – GENERALLY – if one works and the other doesn’t – is it usually a ballast or an end problem? I know the bulbs are OK -I have tested them in other fixtures. I know I can buy four new ends -but I am getting frustrated and wanted to make sure there is no issue I might be missing.

    Thanks,
    Mike

    • Dave Rongey says:

      Hi Mike,
      The factors that affect a fluorescent light fixture are basically the lamps and the ballast but if the lamps are allowed to turn dark and burn out in the sockets then the ballast may need to be replaced. Be sure the lamp pins are fully seated into the sockets and that the light fixtures are well grounded.
      Shine On!
      Dave

  24. Ollie says:

    I have a fluorescent ceiling light fixture in my kitchen. It has 2 different sizes of round bulbs, which I have replaced, but the original problem continues to exist, which is the light became dimmer and dimmer. I replaced both bulbs. The fixture has a constant slight flicker which I cannot fix. Any suggestions? Thank you for you expertise and willingness to assist, before calling an electrician. Ollie.

    • Dave Rongey says:

      Hi Ollie,
      You are describing what is known as a Circline fluorescent light fixture. Be certain that the 4-pin connectors to the lamps are lined up correctly and firmly in place, because those connectors can be tricky. As with any fluorescent light fixture, if the Circline lamps are allowed to completely burn out while in the light sockets, then this may cause the ballast to go bad. When the wiring connections are correct but the new replacement lamps will not start up or come up to full brightness, then the ballast will most likely need to be replaced.
      Dave

  25. amy says:

    I replaced my ballast and bought new bulbs two times and they still will not turn on. Does this mean the new ballast is defective?

    • Dave Rongey says:

      Hi Amy,
      If the lamps are the same which are listed on the ballast label, and all of the wiring connections are correct, then the ballast may be faulty.
      Also be sure the pins of the lamps are in the proper position within the lamp sockets.
      Dave

  26. Jackson says:

    I have a 9.5″ 18 watt T5 light that went out in my aquarium recently. I noticed the bulb was dimmer than normal the other morning. About an inch of the bulb near the base was still lit. I assumed the bulb had gone out so I purchased a new one and am still having the same issue. Any suggestions?
    Thanks

    • Dave Rongey says:

      Hi Jackson,
      First, make sure the new lamp is installed correctly where both pins at each end are all the way into the sockets and making contact after a slight twist. If a fluorescent lamp burn out while in the socket it may also burn out the ballast, and if that is the case then a new ballast may be needed. Also, check to see if there is a lamp starter which looks like a small round silver can about 1/2 inch in diameter and about 1 inch long. Some smaller fluorescent light fixtures have these lamp starters which are needed to start the lamp and bring it to full brightness and sometimes these starters will need to be replaced. Typically these lamp starters are found at one end of the light fixture and they have numbers on them such as FS-2 etc. Lamp starters have two pins on one end and require only about a quarter turn to remove them.
      Dave

  27. Tony says:

    I have two fluorescent light fixtures in my kitchen. One is an old T12 with a starter and a newer T8 fluorescent light fixture that does not have a starter. When I switch them on the T8 fixture comes on, and then goes off when the T12 fixture comes on. I initially thought that the two things were connected, but it must be coincidental as the T8 fluorescent goes off after a few seconds even when I remove the tube and starter from the T12 fixture.
    So, what might be wrong with the T8 fixture? It’s nice and bright for the few seconds that it works.

    • Dave Rongey says:

      Hi Tony,
      Check the wiring of both light fluorescent light fixtures, especially the wiring to the lamp sockets as connected with the ballast. Treat each light fixture individually so there is no wiring connected between the T8 and the T12 with the exception of the circuit power wires. Also, make sure that the enclosures or housings of each light fixture are bonded to ground, where the ground wire is attached to the metal frame of the light fixture.
      Enjoy your fluorescent light fixtures.
      Dave

      • Tony says:

        Hi Dave,

        It was with great hope that I discovered that the supply earth line was not actually fastened into the connection block on the T8, the one that goes off after a few seconds. I refitted the earth and checked that the case of the fitting was earthed using a continuity tester between case and supply earth. I also put a new starter in the T12 and tested. Both lights come on together now due to the new starter, but the T8 still goes off after around four seconds. I’ve checked the earth on the T12 also. The only connection between the two fittings is the lighting main ring, though the spur for the T8 probably comes off the T12 as it’s in an extended part of the kitchen.

        Thanks for your pointers so far.

        Tony

        • Dave Rongey says:

          Hi Tony,
          Make sure that the lamps that are being installed into the fluorescent light fixture are compatible with the ballast. The ballast typically has a label showing a wiring diagram and the numbers of the lamps that are the right for the fixture. Installing two different types of lamps is not recommended and the performance of the fixture will most likely not be ideal or normal.
          Dave

  28. Ray Jackson says:

    I have a circle (12″ diameter) flourescent light in my kitchen. It went out. I replaced the bulb. Nothing happened. It may be the ballast or starter. I don’t know where they’re located or what kind to get or how to change it. I am an industrial electrician but don’t know too much about residential set-ups. Can you help me. If it’s not the ballast/ starter what could it be and how do I correct it.

    • Dave Rongey says:

      Hi Ray,
      Yes, some of the circle fluorescent light fixtures do have a starter which should be mounted into the base of the light fixture, or as you have said, it may be the ballast. If it is the ballast you may consider comparing the cost of the ballast to a new fixture. Also, make sure the four pins of the circle lamp are making good contact into the socket and the socket is rotated into the right position because some of those sockets can rotate 90 degrees and the lamp will not work.
      Dave

  29. Kerrie says:

    We have 2 sets of lights in our kitchen – 4 bulbs each. One light stays on the other is out. I changed 2 of the bulbs and 2 of the 4 lights came on. I purchased another set up of bulbs thinking that might be the problem and changed all the bulbs. Now 1 bulb is partially lit and the other not at all. I did notice while changing the bulbs that the part where you line up the “prongs” and turn to snap into place is missing a plastic piece. I don’t know what that is called to try to replace that, and is it an easy process. I’d be lying if I thought I had a knack for electrical issues, but if it is something that is “easy” and I can find instructions on, I can call someone to try to give me a hand? Any thoughts on the possible problem?

    • Dave Rongey says:

      Hi Kerrie,
      From what you are describing about the light fixture it sounds like there is a problem with one or more light sockets, so the sockets may need to be replaced. Replacement light fixture sockets are available but be sure to get the same one with the same mounting configuration. The process of replacing a light socket is a little tedious, and sometimes is best performed by removing the light fixture so the work can be done at a more comfortable work surface where there would be more control of the light fixture and light socket. Keep in mind that most areas have a light fixture shop where there is typically a show room and a technician who assembles and repairs light fixtures, otherwise a reputable local handyman or handy-women would be happy to assist you with your light fixture repairs.
      Dave

  30. Larry says:

    I purchased T8 4 bulb light fixtures used. I assembled them in groups of 3 on the ground with a separate switch and 1 light in first set and 2 in second would not light until i wiggled the bulbs.I put them up and same lights would not work until i wiggled them Next morning same thing,this is a cold garage.Any help would be appreciated.Thanks.

    • Dave Rongey says:

      Hi Larry,
      Here are some things to check to get your fluorescent light fixture lamps working:
      Make sure there is a ground wire that is bonded to the shell or enclosure of the light fixture.
      Make sure both pins of the lamps are fully seated into position of the light sockets, an indication on the end of the lamp will be visible when the lamp is rotated around into position.
      Dave

  31. Joe Smith says:

    I have an undercounter dual bulb fluorescent light in my kitched. Whenever the cabinet door gets closed, the fixture shuts off. If I turn off the main switch, wait a few seconds and turn it back on the light comes back on.

    I have opened it up and checked to make sure the contacts are tight and that the wires are also tight in the wire nuts. All are fine. The bulbs are new as well.

    Any idea what could be causing this?

    Thank you

    • Dave Rongey says:

      Hi Joe,
      Here are a few things to check or consider for your under cabinet light fixture:
      Be sure both lamps are firmly installed into the socket and the lamp pins are making contact.
      Is the fixture 120 volts? If so make sure the fixture housing is grounded because an ungrounded fluorescent fixture may have an affect on the lamp starting. This is especially true with T9 and T12 size lamps, however it may be true with the smaller lamps as well. Is this a newly installed light fixture? If so check the wiring path and methods and make sure the wiring is not disturbed by the cabinet door movement.
      See more at: How to Install Under Cabinet Lights
      Dave

    • Joe Smith says:

      Dave,

      Thank you so much for the response. This is not a new fixture, it has been working for about 5 years. The pins are tight and the contact is good. It never had this issue before. It is one of three units on the same switch. The others all work fine. Whenever I tap on the unit the lights shut off. Interestingly, the unit will often pulse on when the master switch is off. Dunno if this is a ballast issue. The bulbs are new, the wiring tight and everything else seems good.

      • Dave Rongey says:

        Joe,
        I would suggest going through a process of elimination and start double checking with the obvious such as lamps and sockets and swap lamps with a known good set. It may in fact be a bad ballast especially if the original set of lamps have recently burnt out. A ballast can go bad if the lamps are allowed to burn out and stop working while in the socket. Lamps should be replaced as a new set to start fresh, especially after replacing the ballast.
        Dave

    • Joe Smith says:

      I also verified that the ground wire is there and securely fastened to the fixture.

  32. Tim says:

    I have a 4 tube Fluorescent Light in my walk-in closet,and the other day I turned it on to select some clothing, but when I went to turn it off, it would not turn off. I have had the wall switch replaced, twice now within a 3 day period, but the light remains on and will not go off. Can you please advise me as to what the culprit might be? Would it be the ballast?

    • Dave Rongey says:

      Hi Tim,
      Make sure the replacement switch is sized correctly for the circuit, however the electrical load of a fluorescent light fixture is not great enough to damage the light switch. The wiring up at the light fixture should be examined as well to make sure the connections are correct. Recall any changes to the fixture or circuit wiring which may be contributing to the problem that you are describing with the switch.
      Dave

  33. Dennis Shearing says:

    Can you please show me a diagram for wiring a fluorescent tube with two switches.
    Thank you.
    Dennis

  34. charles smith says:

    Whether my lights will work varies with atmospheric or weather conditions. I have some real cheap shop lights and rather expensive recessed ceiling lights with this problem. If I turn the switch on and off several times they will usually (but not always) come on. Sometimes they all come on instantly and other times I have to work the switch a while to get them all on. I have some other lights that always work properly. They have exhibited this problem since they were new. Any suggestions? I hired a licensed electrician to troubleshoot the expensive lights, to no avail.

  35. Jim says:

    My Kitchen Fluorescent light (2 bulbs) Turned on, then both went out. Wont turn back on and have power. Any ideas?


77 Comments

Thanks for your Comments and Quick Questions!

Please make sure your question is about the topic on this page, which is:
Fluorescent Lighting Problems and How To Fix Them


Comments or questions posted here are open for Quality Discussion and Participation - Spam will be deleted.



*