Why would a CFL bulb dim by itself after 60 seconds?

Question

I have some GE Energy Smart CFL bulbs which are advertised as "Bright from the Start". This is true, except within 60 seconds after I turn the bulbs on, they will dramatically and immeidately become much dimmer.

I assume that this is not the intended outcome, so...

... are the bulbs defective? ... is there something wrong with my wiring? ... is something else going on?

If this were a no-name brand I'd assume a defective bulb, but coming from GE I'd expect better.

FWIW, it's a regular switch on a regular circuit. No 3-way, no dimmer, etc.

Answer 1

The Feb. 2012 issue of Consumer Reports had a sidebar about new hybrid halogen/CFL light bulbs as part of a review of light bulbs. The sidebar includes a picture of a two-pack of GE Energy Smart 75W equivalent bulbs.

These bulbs have a halogen bulb inside the CFL swirl. The theory is that the halogen is used when the light is first turned on, providing instant light. The waste heat from the halogen bulb helps to warm the CFL, allowing it to reach full brightness quicker. The halogen is turned off after the CFL has warmed up, so you're getting the energy savings from the CFL from that point on. The drop in brightness you're seeing is when the halogen turns off.

The CR review said that these bulbs didn't last well in a 2 minute on / 2 minute off rapid cycle test, but were otherwise very good to excellent. It also pointed out that once the CFL fails, you'll have a bulb that lights for a minute, then turns out on its own.

Answer 2

That's strange! You should test the bulbs in a different fixture on a different circuit, and maybe at a different property. You could just use a cheap lamp socket on a cord as a test fixture. How the bulbs react in the different scenarios will tell you if the problem is the bulbs, the fixture/light circuit, or some other problem in your house wiring.

Answer 3

My experience with CFL's is opposite to your's. I usually see them start dim and slowly come up to full strength. The newer "instant on" CFLs (Sylvania) are much faster, but never noticed them dimming after a few seconds or minutes.

Bcworkz gave you a good test using another fixture to test the bulbs. You also could check the voltage at the fixture with an AC volt meter. You should see 117VAC + or - 3 VAC. If other bulbs worked ok in the fixture, I doubt you have a problem there.

Have you compared the steady light output after the bulb dims to a non GE CFL to see if the output is roughly the same for the same wattage rating? The GE bulbs may be brighter at startup as a method for instant on and settle down for continuous run. This may be by design, even though I have never heard of such a method.

Answer 4

check C4 and C0 of the lamp's circuit. Also check C1 and C2 these are electrolytic capacitors which very rarely fail but when they fail their failure becomes A headache for the owner, so get your bulb checked by a nearest TV technician who would further be able to solve such issues.