Audi A4 tail lights come on at night and drain my battery

have you checked your fuses headlights ,tail lights and brake lights are all on one fuse .then if the fuse is ok check to see if the bulbs are all ok.better still replace them.and then do the same as for the fuse for your wipers

the battery to get drain means that you have a power leak somewhere. Check sometimes the light in the boot still on as the off switch is faulty or the door is not closing it. What to do first remove the bulb for a night and on next day starts fine the repair the fault. Also sometimes light might still on current to a very low power where is not spot as it happened to me on a customer Alfa Romeo 147,having power leak on the rear left light very low currency and how spotted,left in a very dark place and noticed. If you think is rather difficult to do something take it to an expert electrician to check every close reason for power leak.

SOUND LIKE YOU HAVE FAULTY BRAKE LIGHT SWITCH.

That's the most interesting problem I've heard all week. I'm pretty sure this has to be problem in the switch that operates the light. Are you positive it's the brake light and not just the tail light? Tail light switch is part of the headlight switch. If you're sure it's the brake light, replace the switch under the brake pedal arm, under your dash. I think this is the problem because unless the circuit is engaged at these switches, it's impossible to activate them from anywhere else. Brake switch is easy. You can do it your self. Headlight switch usually involves removing the steering wheel and is kind of a pain but not too overwhelming.

the cars cpu? its the cars brain? will need to go onto a computer to find out what the codes are

One way to reset the service engine light is to take the negative battery terminal off for at least 25 seconds and hook it back up. The light will go out, if you have a bigger problem than just an oil change it WILL come back on. Get the computer diagnostic test to tell you why the light is coming on if it does come back on.

HI there,

I had the same problem with mine. Managed to determine that it was the rear brake light switch that caused a short. This meant that once the car was turned off power was being drained. We thought it might be the computer module shutting down which can take up to 10/30 minutes. But No. Replaced with a new Brake Light Switch, Problem Solved

It would be best to pull the radio fuse leaving it out for several minutes then replace it. tis may well fix the problem but if it doesn't you can remove the fuse agin knowing it will not drain the battery over night

ALTERNATOR NOT CHARGING AT CORRECT OUTPUT OR YOU HAVE A SHORT-CIRCUIT CAUSING CONTINUAL BATTERY DRAIN...(RELAY)... HOPE I WAS OF SOME HELP TO YOU...

common for the brake lights to stay on but not tail lights are you sure its tail lights ? if it is are the front side lights on ?