OK so I'm at work and my 964 is sat in a covered car park (where it spends most of its working week while I commute on the train).

I get a phonecall from reception saying they think my alarm is going off and its loud,VERY!

Theres a constant monotone pitch coming from my car and on opening the doors (which were locked) it doesn't stop, nor does it stop on deactivating the immoboliser nor starting the engine!

Its currently sat with the battery diconnected, any ideas?



As far as I know its a factory fitted alarm along with a Porsche Immobiliser, theres no remote and the alarm is activated/deactivated via the key entry.

The only time I've heard the alarm previously is if its been activated and the door wasn't shut properly in which case the alarm sounded when I opened the door.

 

it might not be alarm because the alarm once going off normally prevents the car from being started??/ I think any-ways if it where me I would pull the fuse in the fuse box for the horn and see if that stops it ? if it does you have a fault with your horn maybe the horn button some how is stuck on and getting live feed from some where ? relay stuck ?

 

Was the battery dead afterwards? I have had an alarm go off for so long it has drained the battery to the point that it can only omit a monotone sound but I haven't had this happen in the 964.

 

Doesn't sound like the horn as I could sound that seperately!

The battery wasn't dead as I started the car no probs and moved it further away from the officeses before attempting to resolve the problem. I've since checked and the battery read 12.9V

I've read my Streathers bible and the only suggestion seems to be that the alarm control unit has failed, which needs bypassing. Two pins require jumping in order to diasbale the immobiliser

Does anyone have the alarm control unit wiring diagram?

Any other suggestions?

Thanks for the replies thus far

Methinks my car is going to be having a longer stay at work than anticipated

 

Bear in mind that the standard Porsche alarm uses a dedicated horn, not the twin tone horn you sound from the steering wheel.

If you can start the car it would suggest that the immobiliser has reset or is non-functional as the standard alarm isolates the DME relay voltage and hence prevents the fuel pump running.

From memory the alarm also sounds the horn in an on-off-on-off pattern, not as a single constant tone.

I don't think any publicly accessible diagram for the alarm system exists - in the interests of stopping the ******* bypassing it!!! Adrian always said he knew how to disable it but always avoided putting the information on the open forum.

Regards

Dave

 

A couple of observations and solutions for when I have experienced problems with an Alarm that would not go away:

1. you cannot simply "pull a fuse" to disable and turn off the alarm horn. The only fuse is in the control unit under the right seat.
2. I was able to "reset" the alarm by turning the key, in the right/passenger door only, two times in succession in the Lock or Unlock position. Not sure how/why that worked.
3. The trunk/boot light switch was "on" (the bulb was burned out) and causing the alarm to continue, with the trunk lid not fully closed.

good luck

 

Alarm control unit ordered.... 4-6 weeks from germany

Thanks for all your help

 

what year is your car?

 

1990

 

ok, you dont have the alarm module under the pass seat in a 90 model, it is under the hood under the passenger side windshield area. I needed one also, and they are all over ebay for @ $50.00. You also should not have an 'immobilzer' per say. The alarm in a 90 model is primitive as it only works off of the key cylinders and does not have key fobs, etc. When triggered, it stops supply power from going to the DME relay, which obviously causes a no start condition. You can easily check a few pin outs to see if a cylinder switch is causing the problem. Let me know if you want to go further..

 

I bet the problem is one of your door cylinders, when they're disconnected (or dirty) create that weird problem, go back to the car and lock/unlock the car using the key on both doors and from the central button in the console, each time give about 5 seconds in between..
I can create a wacky condition if I unlock/lock too fast.


good luck!

 

I know this thread is very old, but @rattlsnak if you’re still around, I would love to know how to test this. My ‘90 C2 has this problem. No switched power to 87 in the DME socket. I suspect the lock brain is the culprit as the driver’s side door lock kind of fell apart and is inoperable.
Thanks!

 

hey @rcarpen22 I'm still around although I'm not sure I remember how this system works anymore! lol. Send me an email and I'll see what I can dig up!