pearlwhitesix

The low beam HID headlight on the pass side went out last week, so I bought a set of new bulbs from ECS

http://www.ecstuning.com/Audi-C5_A6-...ite/ES2539465/

I replaced both sides on saturday. The next day, the drivers side started acting weird. When cold, it turns on fine and will stay on. After driving for a while, everything is warmed up and hot, if I turn the car off and restart, it fails to turn on. A few times I was able to get the light to turn on after turning the switch off/on a couple of times.

I've done a bit of research and signs are pointing to a bad ballast. Any thoughts? I have the stock Osram bulbs still so I will swap the good bulb back in to see if the behavior changes.

I've also read that using anything but Philips/Osram bulbs can lead to premature ballast failure; of course I found this out after I bought the bulbs already.

Any help is appreciated!

tester123

Bad bulbs can cause this. I suspect ECS would sell such but you never know where it came from or the quality. That's why people including myself suggest phillips bulbs.. osram's are also good.

Ballast failure can happen but it is not so common with stock. Aftermarket is another story. Again, who knows the quality and make... Check ballast wiring/connectors. Swap working old bulb into the defective side. Try to return those bulbs if you can and buy phillips.

GTA_Driver

Bad bulb(s).

Get Osram or Phillips from TheRetrofitStore.

Worldwidebeagle

Had the exact same symptoms on my 2003 AR. Bad ballast. Indie shop used new bulbs, but would only stay lit for a short time. Gave them back the new bulbs, put in a new ballast and the old bulbs, has been working for two years. Drivers side ballast is a bitch.

ECS Tuning-Audi

It could be a bulb. Try swapping back an old one to see if anything changes.

If it does give our customer service a call 1-800-924-5172 ex 134 and they should be able to take care of you.

Best,

Jason

SloopJohnB@mac.com

LOL--it's probably worse on your 2011 but at least it's still covered by warranty unless you've already racked up 50K!!!

Worldwidebeagle

Just got the 2011 avant. Bought because it had 1 year and 12k miles factory warranty left. and my wife was really tired of me replacing something on the allroad each month. Now she has the ar.

Did a lot of research on the ballast issue. They get weak when old and can't ignite the hid lamps. And the older a hid lamp gets, the more voltage it takes to fire. That's why a new bulb might fire for a while an old weak ballast. That is why mechanics advise never to buy a new hid lamp until you switch l and r bulbs to confirm it's the bulb or ballast. The OPs symptoms sound just like a weak dying ballast.

tester123

makes sense.. well, kind of. I should know how these operate because there was a time, when HIDs weren't so common; couple of us were trying to find out exactly how they worked so we could build our own ballasts...

Ballasts can and will get old. Just a fact of life with anything. But, the "higher voltage" you mentioned is not without limits. It will only ramp up in steps based on current feedback. At a set point, it won't fire anymore (same as open circuit). Further, it takes more current to re-ignite a "hot" bulb(one that's just turned off) than to ignite a cold bulb.
From my experience, the ballasts on Audi are some of the best to be honest. In most cases it is usually the bulb that's bad.

Unless, of course, water and other damage, beyond its normal operating parameters... Oh well, I shared my $0.02

SloopJohnB@mac.com

I actually prefer a slightly used executive loaner or whatever…Audi usually warranties them to another two years over the 4/50 and to 100K miles.

pearlwhitesix

Thanks Jason! It is a bad bulb. I swapped sides with the bulbs and the behavior followed the bulb. I will be calling you guys.