I flicked the light switch in the bathroom and only one of the 4
fluorescent light bulbs came on. After about a minute or so, the other
three came on. I turned it off and let it sit for 10-15 minutes and
tried it again. All 4 came right on.
Should I replace all 4 bulbs or is it likely the ballast (is that the
right word) that is going bad?
If these are T-8 fluorescent lamps, there is probably only one ballast.
The problem is likely the lamp or it's connection at the socket.
If these are T-12 fluorescent lamps, there are two ballasts. The problem
is still more likely the lamp or it's connection at the socket.
Sorry, I read it, or at least interpreted it backwards. (dyslexia or
something) That sounds like something flaky with an electronic
ballast.(T-8) Doesn't seem likely to occur with a pair of magnetic
May just be an anomaly, see if they continue to work properly.
What was the temperature in your bathroom? If it was cold in there, the
lights may take a while to come on. Someone may have already mentioned
wiggling the bulbs because in a bathroom exposure to a lot of moisture
could have cause a bit of corrosion on the bulb contacts.
On Mon, 20 Feb 2012 20:05:50 -0600, The Daring Dufas
The house is in south Florida, so it's warm and humid. Plus it's a
bathroom without good ventilation. We were out for several hours. When
we got back, the lights went right on.
Tomorrow, I'll remove the bulbs and check the contacts for corrosion. I
suspect the bulbs are fairly old. It's my mom's house, and she is not
sure when they were last replaced.
Remove all four tubes. With a slightly damp rag, wipe down all the
tubes to get any accumulated dirt off the glass and the ends. Dry
thoroughly and put the tubes back. Not if any have fairly blackened
glass at the ends of the tubes. Replace the tubes. See what
happens. If one light lights right away, note that tube and mark it
somehow. Switch the good tube with any of the other three tubes. See
what happens when you turn the fisture on. Does the good tunbe light,
or does the replacement tube light. If the replacement tube lights,
the ballast is liekly to be bad.. IF the good tube still lights, the
other tubes is probably bad.
The above suggestions are right on especially the one about cleaning the
In damp, humid environments a film of moisture and dirt can "short-circuit"
the electrostatic starting system of rapid-start lamps especially if the
lamps are the T12 type on electromagnetic ballasts.
The simple solution is to clean the lamps. I use Windex and then rinse and
dry the lamps. You can check the lamp pins for corrosion at the same time.
When such lamps are manufactured, they are sprayed with a "dry film" coating
so as to minimize starting problems. When you rinse the lamps, you can
check to see if the coating is working by looking at the lamp and seeing if
the water forms beads and drops rather than a continuous film.
In any case, it's a simple way to check your fixture. If cleaning doesn't
work, then the likely culprit is a lamp or lamps near the end of life.
Ballasts can fail, but they usually work or they don't. Since you said that
the lamp came on after a while, a failed ballast is not the problem.
On Mon, 20 Feb 2012 19:58:45 -0800 (PST), "hr(bob) email@example.com"
Good plan for isolating the failing component, thanks.
I did as you suggested. I didn't see anything that looked like
corrosion. When I put them back, all 4 lit up like they always have.
Maybe something was loose or I knocked off a little dirt.
Thanks for the help.
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