Hot door lock

I have a 95 audi 90 and a weird thing is happening. I sometimes notice that the drivers door lock mechanism gets Very hot. It seems like it happens after I open the trunk…believe it or not. If I start the car anyway, the lock slowly cools down, but it actually gets burning hot. I’m worried it may be a fire hazard. What do I do?

I do not know how the lock layout is done on this car without a wiring schematic but I would agree with you that it could be a fire hazard.

The only thing I can theorize is that there is a voltage issue with the door lock assembly and the solenoid that operates it; with voltage being applied and not released inside the lock/solenoid assembly.
This would require removal of the door panel more than likely to diagnose the problem.

More theory (a.k.a. mild to wild guessing) could be if the locks on this car are operated through a central control module which could be applying voltage and not releasing it.

That’s probably not much help but I would advise that this be repaired ASAP.

I agree with OK4550. Some fault is keeping the power applied to the door lock solenoid. Either a direct short circuit somewhere, or (if the car has such a system) a flaw in the body control module/computer. It IS a risk. I’d begin by getting a wiring diagram and trying to trace the source of the power. Perhaps there is a connector or test point where you can start tracing before you pull the door panel. Being able to trace the voltage will also let you figure out, without having to wait for the solenoid to heat up, if there really is any correlation with operating the trunk lock, or whatever (e.g., phase of the moon).

If the fault IS a short circuit, it is most likely in the wiring harness that flexes through the door jamb into the door. OTOH, if it does correlate with operating the trunk lock, I think it is more likely a module/computer problem (probably not in any software, but in something like output drivers).

Because you do not mention the problem’s causing the door to lock, I infer some info that can help your tracing: the power is applied to the “open the lock” part of the solenoid.

Where do you feel the heat? At the lock cylinder on the outside of the door? At the little lever to manually open the lock, at the power lock switch? On the middle of the door?

I know this topic is rather old, but I just bought an 89 Audi 90 and it does the same thing.

Most of you are thinking that it’s the lock solenoid, but in reality, it’s the door lock heater. See the Audi 90 was actually a very advanced car, and built for rugged climates. They had lock cylinder heaters that would turn on if it dropped below a certain temperature.

More than likely, it is a fault in that system, and not in the locking mechanism.

Interesting. Thanks for new info on an old post.

Sheesh. Door lock heaters – one more thing that can break.