[SilverComet]

So I recently was informed that my right brake light is not operating properly. The running light comes on, but when I apply the brakes the light on the right side shuts off completely. I checked the dual filiment bulb, and both filiments are intact.

Now here's the really weird part, when the engine is off (AC off) and I apply the brake, IT WORKS! :gasp:

I'm not great with diagnosing electrical issues, could it be the brake light switch? I have checked all fuses associated with the rear lights and they are all intact. Any help would be great!

1999 Impreza Outback Sport

 

[1 Lucky Texan]

are the filaments VERY close to touching? If you swap sides with the bulbs, does the problem follow the bulb?

 

[SilverComet]

are the filaments VERY close to touching? If you swap sides with the bulbs, does the problem follow the bulb?

No, I replaced the bulb already, and like I said the brakes light up when the engine is turned off.

 

[1 Lucky Texan]

perhaps there's some debris in the bulb's socket. The 2 contacts might be shorted or ?

 

[H-D]

Sounds like early to mid '60s full size Chevy 'winky tail/brake light syndrome'; caused on those by corrosion in the lamp socket(s), which were two-piece. I generally start on the ground side, checking for voltage drops at the grounds, when weirdness such as this rears its head.