View Full Version : Light bulb issues 2001 A4

03-04-2016, 08:55 AM
Hey guys, I have recently been having issues with the passenger lower taillight bulb. It used to tell me the brake light was out, and sure enough it would be, if I wiggled it, it would work again until the bulb holder would move. But a couple of weeks ago, it went out and I can't get it to light up when sitting.

Every time I use the lights, I get an annoying beep. The brake light function of that bulb works, which is strange... But the idle taillight doesn't work, so I have to run the fogs/secondary lights so I don't get pulled over at night. I have checked for corrosion in the socket and there isn't any.

My second problem, is that up front on the passenger side, the parking light bulb doesn't work, but the passenger turn signal does. This isn't as big of an issue to me as the brake light bulb, but I would still like to correct this if I could.

Thank you in advance!

The car is a 2001.0 A4 1.8TQM Sedan

03-04-2016, 08:55 AM
Same problem but a little different

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03-04-2016, 09:14 AM
Up front, are these dual filament lamps? If so, your likely problem is one filament is toast. Replace the bulb.

03-04-2016, 09:54 AM
Okay, they are dual filament. I feel really stupid now.

I should probably mention that the taillight I have swapped around, and used singular and dual filament that I know work. Does one filament control the taillight, and the other control the brake?

03-04-2016, 10:57 AM

Sorry for all caps, but I was chasing my own dick for MONTHS only to find out that numerous issues across the ENTIRE CAR were simply related to ONE single-filament bulb in my tailight when they should all be dual filament.

03-05-2016, 05:51 PM
Really? The whole light system can be tricked with just a single bulb being a single filament?

I'll be sure to swap the three out that are single filaments that the previous owner used.

03-05-2016, 05:55 PM

Get this. When I had a hidden single filament bulb in my rear drivers side TURN signal.... my 3rd brakelight would be on 24/7, but only when the running lights were on. When I hit the brake pedal, it would get darker. When I hit the brake pedal, the front drivers side TURNING LIGHT would come on. Then randomly I'd be driving and the BRAKE light would illuminate on the dash.... sometimes it would even start flashing. All because a single filament bulb was used.

From what I understand they are dual filament bulbs because they are two systems running through there; the running lights and the turning signals. If you use a single filament, you basically short the entire system out.

03-09-2016, 05:20 AM
Okay, so I bought the new bulbs. Still no taillight on the rear passenger. Brake light still goes on though.

03-09-2016, 05:40 AM
I would check every single bulb on the outside of that car and verify they are dual filament.

03-09-2016, 06:06 AM
Well, the other six bulbs are still single filament in the rear, but I couldn't get them to go in... And then I realized any of the sockets besides for the low taillight bulb are single contact. What bulb would I need then? I bought 7528s. So obviously I got the wrong ones for the other sockets.

03-09-2016, 06:39 AM
Check this chart out: http://www.lightbulbs4cars.com/audi%20bulb%20guide

03-10-2016, 06:26 AM
Okay, I had already replaced the parking light, but the rear lights are all single filament, excluding the stop/low taillight. The bulb sockets that are single filament are only a single contact, so wouldn't it be impossible to run a dual filament bulb?

03-10-2016, 07:43 AM
The rear brake lights I think are dual filament? That website I linked you to should tell you if they are single or dual and what bulb is needed. I'd cross reference every bulb for 100% certain.

03-16-2016, 03:26 AM
The bulbs used for braking are dual filament. Would it be possible there is a bad ground or something on the bulb housing?

03-16-2016, 11:39 AM
Yep. I'm not an electrician otherwise I'd help you trace the short down :(

03-22-2016, 04:46 PM
No worries! I appreciate your help!

03-23-2016, 06:24 AM
I wish, and am surprised, that nobody else has pitched in here.