Alarm self engages and won't stay off when key is on

[SRVYJM]

I have a 1990 Porsche Carrera 4, lately the alarm / door lock engages once I start the engine. I can shut it off manually at the switch on the console, but the alarm will still go off if I open the door when the car is running, like to pick someone up or drop someone off, if they open the door, the alarm sounds. Doesn't matter if I have the doors unlocked or not, it still does it.

Any help on troubleshooting this rather weird problem that just recently started?

[rattlsnak]

Sounds like your alarm module is getting a lock/arm signal incorrectly. You need to check both key cylnder switches and make you sure you have no continuity on the lock and unlock wires when the key is not being turned.

[SRVYJM]

Originally Posted by rattlsnak

Sounds like your alarm module is getting a lock/arm signal incorrectly. You need to check both key cylnder switches and make you sure you have no continuity on the lock and unlock wires when the key is not being turned.

Both key cylinder switches? You mean the ignition key and the two door keys? Which wires are the lock and unlock wires?

FWIW, this only happens when the key is in the ignition. The locks seem to work fine when I use the keyless dongle and the ignition is not engaged.

[rattlsnak]

Keyless Dongle? Porsche didnt have keyless entry in 1990 in 964s.

that being said,

there is three wires going to the door switches. One is permanent ground, the other two should be open circuits until you move the key to lock or unlock which then completes one of those circuits to ground. You can check this at one place at the module. Unplug the module and test pins 7 (br/bl) and 9 (br/gn) seperately. They should not be grounded until you move the key to unlock or lock. (pin 7 is lock, 9 is unlock) Confirm what is going on there and report back... and then we can continue on a path...

[SRVYJM]

Originally Posted by rattlsnak

Keyless Dongle? Porsche didnt have keyless entry in 1990 in 964s.

that being said,

there is three wires going to the door switches. One is permanent ground, the other two should be open circuits until you move the key to lock or unlock which then completes one of those circuits to ground. You can check this at one place at the module. Unplug the module and test pins 7 (br/bl) and 9 (br/gn) seperately. They should not be grounded until you move the key to unlock or lock. (pin 7 is lock, 9 is unlock) Confirm what is going on there and report back... and then we can continue on a path...

Door switches in the actual door, correct? So I have to take off the door panel to get to the switches/module your referring to? That's not a problem, but if the module is somewhere else I hate to do all that only to find the "module" is in the console or something! Thanks for the help thus far, I really appreciate it.

Couple other things that may impact this, the dongle was indeed aftermarket. Installed years ago for keyless entry. Has always worked well so I don't believe its a culprit.

Another item of note is this all started occuring after the car sat for the winter in storage and the battery died. I charged it up and then had it sit for the remaining of the storage with the battery terminals disconnected. Then when I reconnected them and brought the car out of storage it started happening. It's almost like I need to reset something from the battery being disconnected.

[wajidshah]

have a 1990 Porsche Carrera 4, lately the alarm / door lock engages once I start the engine. I can shut it off manually at the switch on the console,

[SRVYJM]

Originally Posted by wajidshah

have a 1990 Porsche Carrera 4, lately the alarm / door lock engages once I start the engine. I can shut it off manually at the switch on the console,

That's what mine is doing too. I can shut it off at the switch too, but if I open a door even with the console switch off, the alarm still sounds. have you fixed yours and does it go off if you open the door with the car running (like to drop someone off or pick someone up)?

[SRVYJM]

Bump. I still have this problem. Any ideas?