Hi. First time posting here.
I have a 1990 tiptronic cabriolet.

I’m having some trouble with my 1990 964 with factory alarm.

I only had one factory key, and it was pretty worn. So I went to a locksmith and had a few new keys made as spares. I tested the new key a few days ago and it worked fine. I ran the Car for about ten minutes, and I locked it back up.

Today I started the car with the new key, (don't know if this is a coincidence with the new key) and moved the car to get my other car out and then when I turned the car off and shut the door the alarm came on.

I tried to lock and unlock the doors, Alarm stayed on.
I restarted the car, Alarm stayed on.
I put it in gear moved it back and forth, Still alarm is going.
pushed the central locking button, Alarm still going.

Tried locking the doors, unlocking, I honked the horn to see if it was a stuck horn, and that beeped but the alarm was still constant.

My ears were now starting to hurt, So I just unplugged the battery terminal and the car is sitting currently with the terminals unplugged.

Do you know what this could be?
How to fix it?
Do you know how to disable it.


I've read some posts about modules and doors not locking, but mine all work, its just the alarm wont turn off.


Today I reconnected the battery and alarm was off. So I figured I'd test the keys.
Both Factory key and new key I made are the same result.
Passenger side door lock works fine without any noise! I can unlock it and then I can use the central lock button to re-lock the car and it arms. No problem there.

The Car can be started that way too with either key. I can open the Drivers door when I unlock the car from the passenger door. Fine.

But as soon as the car goes into gear, the alarm comes back on.

If I try and disarm and unlock and open the car via the drivers door.... Alarm goes off.
Not any flashing lights, just the horn.

It has been raining the last few weeks (Vancouver) and the car has been outside. I read another post where someone was experiencing the same thing on the drivers door with moisture. But there was no solution.

So it's in my garage now with everything open, battery disconnected and I’m hoping everything dries out? (Even though there is no water anywhere)

SUGGESTIONS PLEASE!
Kind of Frustrated

 

can you unlock the driver side door with the key or the central lock button?

 

No. I cant. If I do the alarm comes on. I can unlock the passenger door and then the driver door can open no problem. But as soon as the car is put in gear the alarm goes off.

 

Perhaps the computer requires the drivers door to be opened via key from the outside and not open from the inside thus the alarm?

 

I tried the key in the Drivers door. Alarm goes on as soon as the door is opened.

 

so the passenger side door will unlock with the key and let you in without setting the alarm.

it appears the alarm needs to be disarmed somehow prior to entry.... and the key in either door wont suffice.

is the car supposed to have a key fob to disarm the factory alarm?

 

I bet the door handle alarm wire connectors are not dislodged or something similar. I have the exact same symptom if I open with the key on the passenger door, only the drivers door work ok for arming/disarming.

I assume is the door handle, it is possible the wire to the module is broken, should be as simple as shorting two wires (or ground it/them).

Please report back.. Good luck!

 

For what it's worth, I have a 1991C4 Cab with a similar issue, if I use the key to unlock the drivers side door the alarm will sound and I cannot shut it off from the drivers side by relocking the drivers door or any other means. I can only shut the alarm off by locking the car from the passengers side door. BUT, if I unlock the passengers side door first, then use the key to unlock the drivers side door, no alarm...
I had my local independent repair shop look into the issue. Their assessment was that I needed a new drivers door alarm sensor/switch. As I recall it was a couple hundred bucks plus labor. I have not bothered with the repair yet, for now I just lock and unlock from the passengers side.

Kevin

 

This happened to me, you left the car out in the rain and I'll bet the passenger side footwell and under the seat where all the brains for the alarm are is soaking wet. Go and check, you'll see.
You have to dry the whole thing out, take out the seat it's easier and find out where the water is coming in from-do a search here- there are several places: windshield, sunroof, doors if they don't have the plastic membrane anymore.

Mine is fine now although it went on for so long the horns for the alarm kicked the bucket.

This is a common problem with our cars, water gets in and goes right to that spot or the rear seat sometimes, it did the same on my 73 (no alarm under the seat) so maybe it isn't just the 964s.

 

I had the same thing happen to me. On the 4th of July it was raining and the alarm on my 1990 coupe went off. I had to disconnect the battery. For the next four days it started sounding within moments of reconnecting the battery. I finally had it towed to the dealership that Saturday. On Monday they could not duplicate the problem and it has not happened again. I checked all of the switches and the alarm unit and did not see any problem or sign of water ingression.

If you need to lock the car you can do so. Just leave the truck open and disconnect the battery after you lock the doors. Good luck with this.

 

There is a way to fix. You need to remove the unit, in most cases its wet. I removed both door panels and the box. How it gets moisture in is beyond me. But there was water in it. And the doors. I removed it all and dried it all out. I disconnected the horn for the alarm. I never want it to go off anyways. There is a way to bi-pass the alarm and its discussed on Pelican Parts forum. But you need to have a perfectly working alarm module. My module is now dry,and sealed back with cocking. Its not going to leak. However I just bought a spare too. The Alarm is now off and everything seems OK. So it is a moisture issue and removal is needed. Replacing it is best, and I've been told to seal it as I did or put it in a bag and ensure that the water wont get back in.

 

Thanks for the update! Where was your alarm module located? From your description it sounds like it was inside the cabin?