Audi 80 Intermittent Immobiliser Problem

[jacksticks]

Hello all,

my Audi 80 TDI on an M plate (Feb 95) has had an intermittent immobiliser problem since I got the car in January this year. Basically when you turn the key the immobiliser light flashes then usually goes off after a few seconds. Sometimes the light keeps flashing and if you tried go start the car it would cut out. You can keep turning the key off then on until the light goes and then start the car! It has an MOT coming up so I was wondering if anyone has had the same problem? I have read some threads on here with similar problems. Things to try include turning the alarm/immobiliser off with a key under expansion tank, disconnecting central locking pump and simply resetting ecu by disconnecting battery and reconnecting.

I haven't tried these things yet,

thanks

jack

[Crasher]

The 95 model (S chassis) was the first one to get the legally required transponder immobiliser. The box under the expansion tank and the central locking pump in the boot have nothing to do with the immobiliser fitted to the car when new, these are three separate systems, one of them being an aftermarket part. It is not starightword to disable the factory immobiliser but it can be done. The usual problem with the 8A was the reader coil around the ignition switch. The standard process for repairing this is to use VAG part number 4A1 905 855 B at £141.24 which is a new barrel and key with the reader coil, unfortunately it means two keys. You MUST confirm a low key signal first with a fault code read before changing the lock and the new key has to be programed into the immobiliser box using specialist equipment. As a cheat I have sometimes gently pressed off the rear coil from the new barrel and driven off the old one and then carefully pressed the new one onto the barrel. This way you get a new reader coil but keep the old key. The downside is it could also be the chip inside they key which is to blame and I bet you do not have a spare key?

[jacksticks]

Oh dear! Doesn't sound too good! I have three keys, the two main keys, one with torch button and then I have the second key. I can't see where the chip would be in the keys I have? Maybe this is the problem. If I word up the MOT centre which I know quite well maybe I can get them to test the car knowing eventually it will start! It sounds like a big job and cost to fit the new coil and I only paid £650 for the car. It would be a big loss though as it is like a tank.

[jacksticks]

Sorry meant to add whichever key I use I still have the intermittent problem. Thanks

[Crasher]

The chip is like a tiny grain of rice inside the key and don't go looking for it, the glass ones are extremely fragile, moulded into the key. Don't take this the wrong way but I constantly have to keep reminding people that the used value of a car cannot affect its repair costs IF you have to pay someone else to repair it and especially so if the parts required are only available new from an Audi dealer rather than an aftermarket source. You have a £20000 car, not a £650 car and not only that, it is a 20 year old £20K car and cars get more expensive to maintain as they age, not less.

[jacksticks]

Absolutely right! I agree with you. I have a 1987 XR3i as well so I know about expensive to maintain! Interesting info about the key and the tiny chips. I will look into the garage costs to fit the new barrel and re coding keys. This Audi is the best car I have ever had so I want to get it sorted. Thanks

[zollaf]

luckily my 80 just pre dates the chips and my immobiliser, the one in the boot, is bypassed. great cars but i agree with crasher, its an expensive car and you need to keep these old bangers on the road by 'diy' ing. for instance, i got mine with a blown heater matrix. 2 days to pull the dash and do the job. if i charged that out ( i own a garage) (in wales) it would have cost me like 600 quids, more than enough to buy another car. don't ask what my s4 costs me in time to keep going. lol.

[jacksticks]

Yep, I would definitely attempt to change out the barrel myself but the recoding of the keys is something I would definitely need expert help with. Interestingly I reconnected the alarm in the boot, looks like previous owner had unplugged it. When I locked the car previously I didn't hear the horn beep but now I do. Maybe I just reconnected the horn. This made no difference to immobiliser problem etc! Thanks for all the advice.