bob_man

I am trying to pin down what began as a dead trunk light/trunk motor issue. When the car is off, you cannot manually turn on the rear interior lights or the reading lights. I now see that if the rear interior lights are "dead", so are the trunk lights and trunk motor. When the car is running, everything works: lights, trunk motor, trunk lights - open the rear door and the rear lights come on, etc. When I shut the car off and remove the key, the interior lights do not come on - neither front nor back. When I exit the car, the front interior lights come on normally. I have also noticed that when I arm the alarm, the doors lock and the car chirps but the LED indicators on the doors do not always come on.

Can someone please point me in the right direction on this one? I can't figure how the interior lights might be impacting the trunk lights and trunk motor (or vice versa). Could this be tied to a faulty ignition switch, since the issues disappear when the car is running, or something else, like the convenience system central control unit? I do not (yet) have a VAG so is this a fault that would be recorded?

Thanks in advance.

2004 A8L

bob_man

Still hoping for a little guidance on this one.

I changed the trunk latch but the problem continues. On what should I be focusing next? The CCM (J393)? The ignition switch/module?

Any suggestions greatly appreciated.

bobster1121

im not much help as i am new to this model, i would say though without vag.com its a difficult car to diagnose.
I have just started using carista and that gives a full fault reading diagnostic.
It has worked well for me so it may be an option for you and the outlay is relativity small compared to the full vag.com system.

haggisuk

Without a vcds scan your asking for too much.

until you get a scan done there's little you can do to fault find this problem.

the only thing that I could guess at without a scan is a duff battery. do you have the battery meter in the mmi?

if it's reading anything other than 100% then I'd recommend you get a new battery and have it coded to allow the car to know you have installed a new one.

dvs_dave

Diagnosing an electronic issue without VCDS is an excercise in futility and wallet emptying unless you get lucky.

Without any sort of scan info, the only thing I would suggest is replacing the battery. Marginal batteries often cause random and illogical faults like this.

bob_man

Thanks for the replies. On top of all this, I was greeted with 2 inches of water in the passenger footwell and the passenger seat dead, in the full recline position. Car started this morning, shut it down while I snaked the blocked sunroof drain and now it won't start - dash is dead so I can't see battery meter. However, the radio comes on...sigh.

Jack88

Time to call the insurance company. That much water means quite a lot was almost certainly fried. You would need the proper diagnostic tools(VCDS, $350 for the real working unit,) to make any headway, and even so, that will only identify what has failed. If a lot has failed, getting the replacement modules even yourself could get very expensive.

If you insist on going at this yourself(or have no choice,) before you try powering up the car again, I'd disconnect the battery and get everything as dry as humanly possible. Even condensation can cause issue where water otherwise may not have gotten to at first. While the car dries out, peel back the carpet where the water was sitting and remove the modules located there. Dry and clean those to the best of your ability as well. Once anything and everything is bone dry, reinstall the modules and reconnect the battery, and see what works.

bob_man

Jack88- it started after I dried everything out (shop vac and wife's hair dryer worked wonders). I did not see a module under the carpet on the passenger side so I thought I was safe. I dried out the passenger side fuse box and the convenience CAN. It started right up so I opened the sunroof to work on the drains. I had the doors open for a while but interior lights timed out so I thought I was safe with respect to the battery. I have a charger on the car but still no power to the dash AND the sunroof is open.

I had no idea that a new battery needs to be coded to the car. I am starting to really miss my old A4...

bob_man

Problem solved - CAN link was not fully seated when I replaced it. Car runs...thank god.

Anyone know where the passenger power seat relay/fuse is located? This is still inoperable due to the sunroof drain flood.

Jack88

I am so glad to hear the car works. I was assuming if it got wet enough to not be able to start, that the resulting damage would be extensive. There is a control module under the forward part of the seat, without much protection from spills. That would explain the lack of seat movement. It's under a black plastic cover. Also, there are circuit breakers that can have been tripped.