2000 a4 facelift. recently my right fog light has been working intermittently, IE working every once in a while, i thought the bulb was blown the first time it went out so i didnt think much but then i noticed there was a residue on the housing, thought maybe a bad seal and moisture got in. sooo today i took out the housing and opened it up to find a white residue all over the inside of the housing. the prongs on the bulb looked a little burned, i am wondering what could have caused this? could i have put the plug on backward when i replaced the bulbs with yellow a few months ago? should i stop using my fog lights until i figure out what caused this? ANY information will help. Thanks!

 

I would probably stop using them. Moisture + electricity= bad times.

 

No there was no moisture in the housing. All seals looked good and there was just the white residue that i thought might be moisture when i first saw it. It almost looked like the bulb shorted out but it still works. I took apart the housing, put it back in and now it works all the time. I just want to know what could have caused that and if i have a problem

 

Sounds like it might have been some kind of corrosion from a bad connection.

 

I guess its not as simple as i thought... but if i had put the plug on the bulb backward could that do it? Or can it go both ways? The prongs are the same size

 

Incandescent bulbs such as the typical halogen bulbs used in fog lights have no polarity. So they can be plugged in either way.

 

Well this is a mystery to me. They have worked since i took the housing apart. Must have been a bad connection or something

 

finally figured this one out.... when my right fog light started working again and the left one stopped, i decided to check out the bulbs. of course the yellow bulbs i bought were 100 watts, the old ones were 55 watts. on a positive note i thought i fried the housing but i put the old bulbs back in and they are still working wheww