Avant Central Locking playing up

[Christophski]

Hey guys

Need some advice....

So as the title suggests my central locking is playing up, and it has done since I brought the car however many years ago. I have been meaning to get round to fixing this but never have and since I have had the car back from having some paint work done I have decided to try and do something about it.

I do not have remote locking, its all done off the key. It doesnt have any alarm either from what I can tell.

Key in the drivers door lock will only lock and unlock the drivers door. Nothing else operates from here.

Key in the passenger door lock and boot lock will lock and unlock the whole car.

Since the car has been back with me from paint, if I lock or unlock the car from teh boot or passenger door the pump continues to run for 30 seconds(???) and eventually the rear drivers side door will lock/ unlock depending on whether I am unlocking or locking the car at the time. (This is a new issue as I have said) I am not sure if the paint shop took the rear drivers side door trim off or not.

So what I am really wanting is some advice on where to start looking as I have tomorrow afternoon off work so I thought I would take a look. I have looked at all past threads for some guidance so I am going to check the wires under the carpet in the drivers foot well and near the bonnet release grommet... Any other pointers???

Thanks in advance. (im really not looking forward to trying to sort this one out!)

[UrS4boy]

I've had something similar with my 98 C4 A6 Avant. My central lock pump would run for sometime on opening and closing the locks. The right rear door *seemed* to be slow in responding. But it was just a symptom (not the problem).

This is what I wrote in answer to a similar question on a different forum:

"Like the sedan's trunk lid, the rear lock on the avant is activated by a vacuum solenoid. On this solenoid, there is a rubber boot. With age and use, the rubber boot splits and leaks. At that point, the central locking vacuum pump under the back seat cannot pull enough vacuum to open (or close) the hatch lock.

Photo 1:

Photo 2: Actuator out:

When I first had the problem on my 98 C4 A6 Avant, I thought it was at the connection to the vacuum system (it has the later style vacuum connections) but after buying two new connections (2 on a piece of hose) and them not
fixing the problem, I finally saw the split on the black rubber boot. "Fixed" with bicycle tube patching glue, multiple coats. It worked for awhile but I expected it will fail at some point in the near future. (I planned for a replacement solenoid).

It took some months to fail again. In the meantime, I acquired a good used sedan trunk lock vacuum actuator off a 93 UrS4 that somebody was parting (cost me $5). When the avant lock accuator failed I removed it (again) and replaced the ripped (again) black boot with the red silicone rubber boot off the sedan actuator. Works just fine.

As someone mentioned, to get to the hatch lock actuator, you need to remove the hatch trim. Here is a DIY to do that:

http://forums.quattroworld.com/s4s6/msgs/93572.phtml

Good luck"

Note: All the above relates to C4 avants. I presume that there will be similarities with the B4 avant.

Dave F.

[Christophski]

Cheers Dave.

Just been out in the garage doing another quick job on it and was sat in the drivers seat with the door closed so I thought I would lock it from pushing the pin on the passenger door down, the drivers one wouldn't go down to lock and I could hear something inside the drivers door hissing. Sounds like there is a vacuum leak in the door somewhere for me to start off with. Wonder where this is and what it does once found and fixed! I know the paint shop had the door apart to take the handle and wing mirror off!