On my prior 928s I always had the rear hatch release had a problem where the release wears out and figured out how to fix it.
BUT on the '91 GT I now have I can't figure out what's wrong.
It will open and close fine for some days and then suddenly it will start releasing over and over again. It will keep on going until I close all doors and then stop. But then I am either in the car with an open hatch or out. So once I open the door it will release once again. It will take a couple of minutes of opening door closing hatch, opening door closing hatch.... and then it goes away. It will happen by opening from either side and is completely irradical.
Anyone has a clue what this might be? It looks like the lock and release mechanism is new, but I have no record of replacement.
regards,
Sab.

 

In my 87 S4 the hatch release is tied to the interior lights.(in other words the interior lights must be triggered in order for the hatch release to open the hatch)

I had a similar problem, but it was tied to an aftermarket alarm system. Do you have an aftermarket alarm system?? If you do it could be causing the problem.

A quick fix would be to disconnect the release motor (there is a connector very near the motor, but your auto release would not longer function????

Thats all I can offer

 

I have a similar problem caused by the driver's side release. It will cycle until I turn the release button. Sounds like we both have the same short.

 

Sab,
As David says the release is only supposed to operate when the door contacts are closed (when the doors are open) technically its not the interior lights since these are on a delay (at least on the GTS). Also the motor has an interlock so that once its triggered it will complete one full unlock cycle before it stops. Typical hatch cycling symptoms implies its likely the motor 1 cycle interlock is at fault. This is a secondary switching mechanism built into the motor - once you trigger the hatch motor - it self powers itself for 1 whole revolution - if you are still pulling the switch it will start another revolution & run until the end of that cycle...

If the interlock is failing could be the little gap intended to break the circuit after it completes a full revolution got smeared with metal from the rest of the track and causes the motor to run continuously - once this is triggered it will usually continue to run but may cut out intermittently.
You will have to dissasemble & clean the mechanism for the motor... or find a replacement...

It could also possibly be the pull switches? do you have 2 switches one each side? if so open the panels and disconnect each of them one at a time and see if the problem goes away. if you only have one - take off the connectors and connect them together by hand to simulate pulling the switch - then disconnect and see if it behaves OK. If this is it then try dismantling the switch and cleaning with switch/contact cleaner.

What you said that it stops when the doors are closed and start again when you open a door seems odd - this is not behavior I'd expect from the intrelock since once triggered it will run independant of the door status - this may suggest a switch issue - but usually low power switches like this reliably go to the disconnect state...? I'd check the switches first - they are both easily accessible.

Good Luck

Alan

 

Sab,
I looked back at some notes and I think Alan is pointing you in the right direction. My problem was as Alan wrote, I had a "closed" switch because of a poor install of an "add on" alarm wire. Because the switch was closed, every time I opened the door the hatch motor would cycle.

Check your pull switches first, and go from there.

Good luck
David

 

Sab,
I had exactly the same problem, especially when it was nice and warm. Here is the cause and my fix.
The rear hatch release motor works just like a wiper motor. Once you activate it it does one full revolution and stops. What happens is that the gears run so easy and smooth, that they continue to move the electric motor for a little even after there is no current flowing anymore. This is enough movement to activate the switch inside the relase motor and let it run for one more revolution and one more, one more one more (inertia) .
This happens as long as the electrical lines are "hot". Only if you close the door the current is completely interruptted and the motor finally stops.

Here is Schocki's solution:
Take the motor out, open the "gearbox" fill it up with grease. This grease will just cause enough friction and lubricate simultaneously to make the motor stop at the correct spot. I did this about 5 months ago and it worked just fine. Try it it is a cheap fix and a good reason for a afterwards

 

Schocki,
You made me check the factory manuals... yes actually the rear unlock motor only runs when the doors are open. However I don't think it has anything to do with how smoothly it runs - I'll bet it ran smoother when it was new - Anyway it really is as I said above - take the motor apart and clean the contact track. It probably is not the switches - like I said they rarely fail "on".

I was not clear because I have had to totally rewire my hatch release motor to add remote release with my keyless entry. The wiring that disables the motor when the doors are closed is an obvious problem for remote release when the car is locked - so my hatch behaviour no longer matches factory - my mistake. It almost certainly is the motor. Repair is very reasonable to do yourself. Reinstallation is not hard - mark the position vertically before you remove the motor - aids in reassembly alignment. Oiling the motor only works if it actually flushes the electrical contact track - just go straight to cleaning it and then apply some non-conducting grease for lube.

Alan

 

Alan,
The first time I took the motor out I cleaned the tracks and nothing changed. Sab lives in Florida and I would bet that his problem is temperature related. Mine started once we hit about 90 here in Texas.
I just used standard high temp grease for the gears and since than it is perfectly fine. I think that the friction inside that little gearbox goes down with time, just like a broken in car and engine at 60000 miles is faster on the Autobahn than a brand new one. That's a fact
However I think it is a cheap and non time consuming fix and would give it a try before buying a new motor

 

Lemme try this one more time. I have the same problem. In MY case it goes away when I rotate the **** on the driver's side because I have a short in the switch when the **** is in a certain position. You might want to try that before you take anything apart.

 

Thanks for the suggestions, I will look at both the switches and the motor assembly.
I don't think it is heat related, since it has happened as well in the cool days we recently had. It is really annoying though and must be resolved. It certainly only happens when I am in a rush.
regards,
Sab.

 

Sab,

I am really sorry that you are having problems with the GT. Since I was involved, I feel partially responsible, so in the interest of fairness, I will give you your money back on the car and take it off your hands, hatch release problem and all...

The most common problem with the hatch release continuing to run is as Schocki suggested - the release motor runs fast enough to overrun the gap where it is supposed to stop. His repair method will usually work.

But - the usual operation is that you pull the button - if the door contact switch circuit (brown/white wires, switched ground) is grounded (door open) the release motor start running. You release the button, cutting off the power supply to the motor - but as soon as the motor started, it gets power from the second circuit, and continues to run until the output shaft gets to the correct point (hatch release flap down, so that the latch will lock the hatch again), at which point the little cut-out interrupts the second circuit, and the motor stops.

Once the motor moves from its rest position, it makes no difference whether a door is open or not. Closing a door won't stop the motor from running after it starts.

Since closing a door will sometimes stop your hatch release, it sounds as if the pull switch is sticking in the on position. See if the release problem ocurrs if you use the passenger door release button.

 

Hi Wally,

ha ha, even with such a significant failure as the hatch release i will hold on to it for now...

I haven't had the time to take it apart yet, but it happens when releasing on either side, soit does not seem related to the release *****. But I can stop it by closing the doors. If I only close the door once it will keep on going, but if I close the door a couple of times (or play with the light trigger switch) it will ultimately stop. Maybe it has to disconnect power just at the right moment for the motor to stop at the right place...

 

Sab,
Taking the motor out is a piece of cake. Git'er some grease in da gears and it will be just fine