I've got a 2002 a4 1.8t automatic. Got in it the other day, put key in, turned it and nothing. Does not attempt to crank over, no sounds at all. all of my dash lights, radio, windows and door locks are working, however they won't turn off either, with or without key in it. Had to disconnect battery in order to cut power and not kill my battery. I have already boughta new ignition switch and replaced that and it didn't change a thing. Key doesn't get stuck, and doesn't turn 360 degrees. But will not start car. Not an immobilizer issue as I've been thru that before. Please help! All fuses in panel on drivers side are good. Any other fuses or relays I need to check?

 

Chris, I am having the same problem, 2003 A4 Quattro Auto. although my lights do turn off when I shut the doors. Replaced ignition switch, replaced starter have 12 volts from switch to starter, checked all fuses beats the hech out of me. If you find anything usefull please let me know.

Thanks,
John

 

Sounds like a problem with the Onboard Power Supply Control Unit. As the name suggests, it provides the power supply to lights and various electrical systems in the car. It's possibly malfunctioning internally. Try unplugging the connectors one by one. It's located up under the drivers side under dash trim panel.

 

John,
I've been beating my head against the wall, and i've searched all over online and can't really find a definite solution to the problem. Actually can't find anyone that has the same type of symptoms except you. I've replaced the ignition switch also...and it didn't change a thing. I'm thinking that it could maybe be the tumbler inside the ignition..? In my case the car is stuck in accessory on (so it seems, like if you wanted to just sit in the car and listen to the radio but not start the car) ...so the only way to get the dash lights and all other electronics to shut off is to disconnect the battery. The key goes in and comes out clean also. I've got the lock cylinder off last night, before i buy any more parts i'm going to check and make sure relay 50 is good which i believe is between the ignition and starter (from research) if everything checks good I'm going to replace the whole ignition under the steering wheel (silver metal cylinder) and hope by putting my lock cylinder on that i won't have to re key anything. I'll let you know how that goes...Seems we are the only help for each other at this point...Really don't want to take it to the shop down the road for $95.00 an hour but it may end up coming to that..

 

Finally solved the problem. And found my hard start problem in the process. But the problem was inside the barrel of the ignition, the pin that goes into the ignition switch and turns it was snapped off, so it wasn't turning the ignition switch at all when I turned the key. For now I can start with a screwdriver in the ignition switch as long as the key is in the ignition.. Hope it helps you John. let me know if I can help