Central locking problem - not Comfort module

[mejtaylor]

I've got a problem with my central locking on a 1997 1.6 Mk4 Golf.

Symptoms:

Headlights on buzzer doesn't work
When locking the drivers door with the key (it doesn't have remote locking), all the doors lock, then all the locks except the drivers door pop up again.

The electric windows and mirrors work.
The puddle lights work.
The interior lights work.

I spent ages taking the drivers door lock apart and checked all the microswitches, both mechanically and with a multimeter, and it was all fine.

As the headlight buzzer doesn't work, i thought it might be the comfort module, so I changed this for a new (well, from a breakers yard but it had been guaranteed as working). The problem was still there.

My next thought is that the drivers door is fine, but if not all the doors are recognised as closed, they will pop up again.

I've also got an A4 and have scanned it with vag-com - which works fine. Using the same lead and laptop i can't seem to connect to the golf to get any fault codes.

At the moment, i have to lock the drivers door with the key, then go round and lock each door by pushing down the knob.

It looks like all the wires that come from the lock module go into the electric window motor - if there is a problem with this could it cause the symptoms i am seeing?

Any ideas? It's driving me nuts...

[herby0001]

You've done some thorough work! The fact you can't connect to the ECU using VAG-COM sounds very suspicious. If it's playing up in some way, it could be causing other modules to misbehave.

[ini]

Should not cause issues, but do you have an aftermarket head unit?

[herby0001]

Good call ini. Now I remember that aftermarket headunits have caused weird electrical problems.

[kenney]

It looks like all the wires that come from the lock module go into the electric window motor - if there is a problem with this could it cause the symptoms i am seeing,the answer to your question is YES

[mejtaylor]

Thanks guys - yes it does have an aftermarket head unit. I've still got the original one so i might put that back in and see if it cures anything.

This weekend i'll try swapping over the window motor to see if there is any improvement.

I had a thought (and then couldn't believe I was so stupid) - the interior lights are supposed to come on when each door is opened, so i tried each door in turn and the interior lights came on for every one apart from the rear drivers door. Looks like i may have narrowed the problem down to this door, so I'll check the lock mechanism at the weekend.

Just a thought about the headlight buzzer (if anyone is still reading..) - I know on MK3 golfs the buzzing noise was made by a relay under the dash - is this the same in MK4s? It might be as simple as a blown relay..