fluorescent light questions

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Forum topic by JesseTutt posted 10-04-2012 06:49 PM 4346 views 0 times favorited 31 replies Add to Favorites Watch
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854 posts in 2079 days

10-04-2012 06:49 PM

Topic tags/keywords: question fluorescent lighting fluorescent problems

I use 4’ dual tube fluorescent lights in my shop. They are 40 watt and have the two prongs on each end. As I prepare to replace the burnt out tubes, several questions popped into my mind. I am hoping that you can help me understand what is going on.

Of the 12 fixtures in the shop 4 never give me any problems. The remaining have problems. Some have just stopped working.

Others will work for some time and then stop for a while and then start again. I would think thermal problem but, sometimes a fixture will work all day every day for a week and then start / stop working at random periods for a few days and then work for a long time.

Many that are not working will start if I wiggle the tubes. I might have to remove the tube and put it back in. I am wondering if I have a dirty contact between the tube and the socket.

Some tubes will develop a black section along one, or both, ends. I always thought this was an indication that the tube was about to fail, but I have had tubes with black work all summer with no problems. Other fixtures having problems may or may not have tubes with black. There does not seem to be any correlation between tubes with black and fixtures not working.

Any insights you have would be appreciated.

-- Jesse, Saint Louis, Missouri

31 replies so far

View grfrazee's profile


388 posts in 2109 days

#1 posted 10-04-2012 06:59 PM

How long have you had the fixtures? It’s possible the ballasts are burning out.

-- -=Pride is not a sin=-

View MedicKen's profile


1612 posts in 3431 days

#2 posted 10-04-2012 07:01 PM

The fixtures that are not working sound like a ballast problem. The ballast is the starter for the fixture and is located under the panel between the bulbs. If these are older lights its probably time to replace the ballast. Do you get any humming from them? The older ballasts are know for an annoying hum. They are easily replaced. When you go to get new bulbs look for the highest color rating you can find. They will be closer to natural light as opposed to the cool white bulb. IIRC the bulbs you want are C95 but I could be wrong on the number. There should be a number printed on the bulb and or box stating the color rendition. The higher the number the closer it is to natural light

-- My job is to give my kids things to discuss with their

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Clint Searl

1533 posts in 2330 days

#3 posted 10-04-2012 07:02 PM

You need new ballasts.

-- Clint Searl....Ya can no more do what ya don't know how than ya can git back from where ya ain't been

View Jacob's profile


85 posts in 2611 days

#4 posted 10-04-2012 07:02 PM

When the lamps flicker or take a long time to turn on, the current is either insufficient or not constant. This could mean their is an issue with your ballast or connections, but its related to the current. Fluorescent s have large ballasts in the fixtures to tune the electricity to the proper level, check the connections there, and the connection to the fixture were the pins contact. Also, maybe cleaning “socket” is not a bad idea.

-- -Jacob Turetsky, Industrial Designer

View Grandpa's profile


3259 posts in 2644 days

#5 posted 10-04-2012 07:06 PM

I vote ballasts also. The black ends usually indicate the bulbs are getting weak. If the ballast is getting hot it might not be able to send the electric flow through the tube. Replace the ballast and the problem should go away. Go ahead and change to the electronic ballast and energy effecient bulbs while you are doing this. This is a job a homeowner should be able to do if he or she is a little bit handy. Be sure to unplug the unit or turn the breaker off. You currently have the regular flourescent unit that operate best in temperatures above freezing. Cold weather units have only one contact on the end and cost a BUNCH more. The will fire in below freezing temperatures and they work longer in those conditions if you have those.

View HorizontalMike's profile


7749 posts in 2883 days

#6 posted 10-04-2012 07:20 PM

In addition to the ballasts mentioned by many, I would AVOID the use of any lower wattage “Econo-bulbs” as these always gave me fits when the temperatures dropped. They do not start in lower temps. Buy the highest available wattage available. You might even try moving to higher wattage ballasts as well. I have the old T-12 8ft dual fixtures and when I got rid of the 40w and replaced with 75w my issues went away.

-- HorizontalMike -- "Woodpeckers understand..."

View Charlie's profile


1100 posts in 2255 days

#7 posted 10-04-2012 07:34 PM

I started replacing a lot of flourescents with 6 inch can lights fitted with LED bulbs.
Search for ECO-575L. Prices can vary quite a bit, but the 6 inch can fixtures are cheap and these go right into a standard Halo 6 inch can.

There’s an expense involved to be sure, but if you are replacing ballasts and/or fixtures, it’s worth a look. I just redid my hole kitchen with them. I’ve been putting them in the basement, the garage, the shop. They start immediately when it’s cold (it gets cold here). They are cheap cheap cheap to run. They won’t burn out for about 20 years hehehe. And I like the LIGHT better than any of the flourescents. It’s more natural. Kinda like working outside.

Just thought I’d toss it out there. This brand is made by Cree Lighting and Cree does LED lighting right. (No I have absolutely no connection to the company)

View MJCD's profile


540 posts in 2340 days

#8 posted 10-04-2012 07:37 PM

The 40-watt bulbs are probably the older T-12s, which are fine – the ‘eco-bulbs’ are T-8s, and they’d be the 32-watt you see in stores. The T-8s ballasts tend to be quieter in cold weather. I agree with HorizontalMike – no one has gone blind using too much light in the shop – mine could be used for a landing strip.


-- Lead By Example; Make a Difference

View HorizontalMike's profile


7749 posts in 2883 days

#9 posted 10-04-2012 07:46 PM

Oops, I probably mis-spoke. The lower wattage were probably 8ft 60w vs the higher 75w. All I remember is the lack of cold starting and that HD phased them out because they were actually NOT economical according to the newer standards/regulations.

-- HorizontalMike -- "Woodpeckers understand..."

View JesseTutt's profile


854 posts in 2079 days

#10 posted 10-04-2012 08:43 PM

Update: for the fixtures that were not working, I removed the bulbs and used 320 grit sandpaper to clean the contacts. This fixed one of the bulbs. For the rest I put new bulbs in and they are now working.

The fixtures are the low cost ones from Home Depot.

Some fixtures I have seen in the past have the large transformer (?) inside of the fixture and a small can that plugs in and turns.

-- Jesse, Saint Louis, Missouri

View Bill White's profile (online now)

Bill White

4909 posts in 3929 days

#11 posted 10-04-2012 09:21 PM

Sounds like you have a fix, but T-8s are what I have. I’ve replaced 5 of 8 ballasts (at Lowe’s cost). So far, no more probs. The Chinese electricals…..........................Oh well.
You want egg roll with you (no typo) lights? Shut up and eat it!!!!


View brtech's profile (online now)


1028 posts in 2891 days

#12 posted 10-04-2012 09:30 PM

My shop is mostly lit with those basic $20 dual 4’ shop lights from the big box.

I had my garage redone this year and, on the advice of the contractor, we put two 8’ HO fixtures in. I was BLOWN AWAY by how much light these suckers put out. It’s BRIGHT, really bright. They come on right away, no flicker, no hum. Definitely worth the price difference, which is considerable. I think you are close to $100 for a two light 8’ with HOs. They sell the fixture without the bulbs, unlike the 4’ shop lights.

I’ll be redoing the lighting in the shop, right after I finish the shelves, the blanket chest, build the new bench, get the jointer back in business, ....

View longgone's profile


5688 posts in 3277 days

#13 posted 10-04-2012 09:31 PM

I have been replacing mine with the newer lights that use the electronic ballasts and have been repolacing the bulbs with the daylight bulbs…Their light is much better and allow me to see more details. No problems with these as I had with the older flourescents.

View WoodKutter's profile


29 posts in 3436 days

#14 posted 10-04-2012 09:47 PM

Jesse, The light fixtures you have are quite old. The T12 ballasts in them generate a lot of heat. The black ends of the bulbs are caused by the heat generated in the fluctuations of current caused by the old ballasts. It will cause the bulbs to burn out prematurely. The fixtures on which you moved the bulbs or took out and put back in for them to work have weak ballasts. The ballasts are not putting out enough to fire up the bulbs. By moving them, you cause an arc at the lampend which spikes the current slightly. Once the bulb lights up, it takes very little to keep it lit. The fixtures which come on and go off sporadically have ballasts which are dying. They over heat, shut down, cool off, come back on. They may stay off for days, then one day start working again for a few days. Sometimes they strobe and drive you crazy.

The problem you will have with updating those old fixtures to T8 ballasts and bulbs is that the wiring colors are different. The T12 ballasts will have 2 yellow wires, 2 blue wires and 2 red wires. The T8 ballast will have 1 red wire and 2 blue wires. Also you may have to change the wiring in the fixture. Some T12 40watt ballasts are wired in series and some are wired in parallel. It is not hard to do but you need someone who knows how. A lot of times the wire insulation is brittle and will break when moved. If you know someone who can show you what to do on one fixture, you can probably do the rest yourself.

My advise would be to replace the entire fixture with a new one. Often times you can buy a whole fixture for about the same or less than the cost of a ballast. The ballast went out in my kitchen light and I purchased a new fixture for about $10 dollars more than the ballast by itself. And it was a nicer light fixture than the one I had.

Good Luck,

View teejk's profile


1215 posts in 2653 days

#15 posted 10-04-2012 09:56 PM

I think T12’s are going to be outlawed soon according to the newsletter I got from my elec CO OP. I started using T8’s (32w) years ago (0F start, seem to last much longer and the light output seems to be as good as the old T12s). But back to the question…T12 replacement ballasts will cost more than the fixture! And just something I heard…electronic ballast failure is often related to poor grounding of the fixture.

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