I have 3 identical fluorescent fixtures in the garage about 15 years
old, 2 bulb 4' rapid start. A clue to their usage is that none of them
had had any bulbs changed in their life.
One of the units showed intermittent flickering sometimes one bulb was
good/bright, sometimes dim, the worse/dimmest bulb had a dark spot at
So I changed the bulbs, with no improvement. Used another new bulb.
Same thing. Took two working bulbs from the other fixture and put them
in. No improvement. I began to suspect something was wrong with the
ballast, but I wasn't smart enough to do any troubleshooting. All I
have is a little volt/ohm meter I use to troubleshoot computer power
So, I went to Home Depot and bought a ballast aided by an experienced
sales person who understood what fixture and bulbs I had. The new
ballast was not as 'fat' as the other but was the same length and color
coding of the wires.
I disassembled the fixture/ballast and replaced the ballast using wire
nuts acquired during the ballast trip and reconnected, reassembled, and
resecured the ceiling fixture.
Now I don't know if my original ballast was good or bad and/or if the
replacement ballast is good or bad. I would like to do some of the
diagnostic testing I didn't do during my original guesstimation that it
was/ must be/ the ballast.
How can I:
- benchtest my old ballast I removed
- test the integrity of the new ballast installed
- troubleshoot my malfunctioning fluorescent
If I could satisfactorily prove to myself that the new ballast isn't
good, then I could return it; but under the present conditions I have no
clue what is wrong.
Swapping bulbs that work from a working fixture and swapping bulbs that
don't work from another fixture is a real good test.
A black end on a fluorescent tube generally indicates the filament is
not heating. Might be burned out (try measuring resistance between
pins). Could be bad connection at socket or wires connecting to socket.
Could be bad ballast, but that is least likely.
Even with the same color wires, the wiring may be differant. The normal
black and white wires should be the same as they go to the voltage comming
in. The wires going to the bulbs may not go to the same place as the same
color on the new ballast. There should be a wiring diagram on the ballast.
Also double check that the words on the ballast match the words on the bulbs
as they may be differant. There are many kinds of ballasts and bulbs that
True but when it functioned the same as the old, the probabilities went
way up that the ballast wasn't/isn't the problem and the new one was
installed correctly and is ok...
In general, the symptoms are symptomatic of quick-start fixture w/
bad/missing ground or missing/improperly installed reflectors that are
needed for the req'd capacitive starting field...
I'd suggest the following page to the OP...
Why mess with it? A whole new complete 2 tube fixture is under US$20
(at least it is at my local Lowes). It's an easy installation, and
only 2 wires to mess with. In my case I modernized with a nicer
looking fixture and the new slimmer instant on tubes.
I thought fluorescent fixtures had to have a good ground to work
properly. wouldn't that be 3 wires?
Get free backup service using Drop Box
Access your files from your smartphone or tablet
Bonus space provided using this link: http://db.tt/RIONkfbZ
It's almost certainly _not_ the ballast (prove it to yourself; put the
old one you took from the troublesome fixture and put it in one of the
working fixtures. Odds are the problem will stay w/ the old fixture.
Did you look at the troubleshooting guide at the link I posted? I still
expect the most likely is the ground isn't what you think it is (as for
how good or the reflector(s) aren't grounded or close enough to the tube
in the bad one). Does it light or change characteristics if you touch
the tube(s) while it's on? If so, that's pretty much conclusive.
I had actually looked at that guide in the beginning before I removed
the fixture and replaced the ballast when I was trying to figure out
whether or not to replace the ballast.
This is the same ground, big fat ground with the power, which is
securely 'bolted' with a nut onto the fixture that has been working on
the fixture for 15 years. We would have to imagine that something has
'gone wrong' with the ground wire's grounding condition. I don't even
know how to test that.
No the light characteristics does not change.
Presently the light characteristics, new ballast, *old* (original)
bulbs, are that the light is not flickering or variable, but that both
bulbs are very 'dim' compared to the other lights.
The black ended bulb is dimmer than the other 15 y/o bulb.
With 2 brand new bulbs, the 'brightest' light is less than 1/3 as bright
as the old lights and the other light is mostly very dim but a little
brighter on one end, but still less than half as bright as the 1/3
bright bulb. There is no flickering and no variability when I 'fool
with' the bulbs.
I'm puzzled about this bulb to bulb discrepancy with the new ballast.
It's not hard to conceive of the ground connection having developed some
corrosion at the fixture end particularly in a garage or even a
connection at the outlet where the fixtures are wired/plugged in.
Also, the ballast must make good contact for grounding as well. I'd try
a little emery cloth to shine up the contacts and check all connections
for being bright/tight first.
Are you sure you have the proper tube designations?
Also, it's possible w/ time the lamp contacts are dirty/loose and/or
have some corrosion as well.
Have you checked the actual supply voltage to be sure there isn't
something wrong w/ the supply--perhaps there's a loose or
high-resistance connection in the circuit itself.
The appearance of the ground in the ceiling power connection is
relatively shiny copper, no corrosion. The bolt and nut are not
corroded. I can't imagine a discontinuity between the ceiling ground
and its connection back to a breaker box ground, nor a breaker box
ground problem. That wiring is off a subpanel inside the house. The
location of these garage lights are a long way from 'outside' - the
garage doors are always closed, no weather gets inside.
I would like to repeat that the two sides do not perform identically
with the old or the new ballast. One side is almost not lit at all and
what lighting there is, is on about 8" of bulb, while the other side is
about 1/3 or 1/4 as bright as normal and uniformly distributed
throughout the length of the bulb. If I switch the bulbs, the same
side, not the same bulb, is as described.
Yes, except that the newer bulbs are 34W and the old bulbs are 40W.
The lamp contacts are clean to appearance and the problem does not
change with twisting the contacts around.
I was going to work on/ measure/ the voltages (and resistance) at the
ballast as soon I found some information beyond my knowing what the
house voltage should be. The voltage at the ceiling fixture in question
is bound to be the same as the other two, they are all on the same circuit.
I think the voltages that can be checked are those of the house current
and also the output of the ballast. Also I think the resistance across
the ballast (somewhere) is supposed to be zero. I'm trying to find some
docs on that.
If there is some kind of ground problem here, I don't know how to
find/prove it. The appearance and the physical security and overall
'beefiness' of the ground are all strong. It looks like a serious ground
of good integrity and strong connection.
I have examined the specs in fine print on the installed ballast and it
is like that of the removed one.
If I had to eat this ballast and disassemble a complete fixture which
costs less than the ballast I bought and would be eating, it would be
necessary for the fixture to have tombstones with slots which match the
ones on my fixture. I don't really like that idea.
I also don't like the idea of swapping out a ballast from an existing
working ceiling fixture. What I really want is some hard numbers on the
installed ballast which satisfy the expected voltages input and output
and resistance across somewhere on the ballast. I have no way to do
frequency checking of the ballast output.
Have you actually taken the ground connection loose and checked it or
simply looked at it? Just because it looks good on the surface doesn't
mean there's not a resistance layer between the mating surfaces or a
layer of paint or whatever.
Doesn't say there is, but unless you check you can't rule it out for
absolute certainty. Same is true back to the point of the connections
to the good fixture(s).
That still sounds very much like the reflectors or a bad ground or
connection or the contacts at the faulty. That with a new ballast the
same symptoms appear (iiuc) pretty much eliminates the ballast altho I
still note the need for it to be well grounded and if there's a problem
there on the fixture side it could well remain for both. Did you make
sure there's not paint or dirt or whatever preventing a good contact or
just toss the new one in where the other one was?
Well, when you won't do the simplest of easy tests to confirm where the
problem goes, it gets pretty hard to diagnose when you reject both the
chances that there might be a problem w/o actually checking and the
chance to see if the problem follows the ballast or is at the fixture
Still really haven't answered the question or indicated you took the
Make sure there's bare metal between the two mating pieces not just the
edge of a hole and use some emery and/or find sandpaper and polish off
any possible surface layers.
You indicated in another posting you're using very old tubes; have you
tried a newer tube perchance? Have you tried the above cleaning on the
pins of the tubes to ensure they've not oxidized over the years of
storage? (I have no real clue on aging of fl tubes but given what
appears abnormal situation I'd look for possibly unusual fixes as well
altho it still seems should be relatively straightforward.)
I don't know that you can test the ballast w/ just a VOM; I surely don't
know any spec's to tell you. I judge that if the new and the old act
the same the likelihood it's the ballast itself is quite low -- unless
it is the connection or the power in; I think that's barking up the
wrong tree meself.
W/ all fixtures I've had, I've never had to take one down to swap
ballasts so I don't quite follow why that's such a problem.
The original design of the ceiling fixture was to affix the ballast to
the fixture with a screw/bolt on the top side against the ceiling and a
smooth round 'nut' (I don't know the name of that kind of fastener) on
the down side exposed after the enclosure for the wires is removed. I
didn't change that design/fastener (yet), so one has to remove the
ballast by removing a bolt from the side of the fixture against the ceiling.
In addition to that inconvenience, the screws for the toggle nuts
securing the fixture to the ceiling are on the other side of an
enclosure for the tombstones, so both of those enclosures need to be
removed to remove the fixture to remove the ballast. The enclosures are
snap-in, so the sides of the fixture need to be spread apart to snap
them out; which would be easy in the middle of the fixture's length, but
of course this prying is on the ends where the metal is joined, so it
doesn't want to spread there.
This fixture does not have a reflector.
In any case, I have more toggles and the fixture is off the ceiling
again so that I can not only bench test it down instead of on the
ceiling, but I can also remove the new ballast and replace it (see
below/later post) and I also now have the ability to connect the ceiling
fixture on the bench to test it for working condition.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.