antlee928

Ok. So I have been having some intermittent problems with my factory alarm system. The ONLY "pattern" that I have been able to observe is when the car is hot (sitting in lots of start/stop traffic or on hot days (winter here at the moment) that seems to trigger the following symptoms:

1. Upon parking the car, stopping engine and removal of ignition key, the alarm goes off as soon as I exit the car i.e. open the drivers side door;

2. The car is parked after some running around not locked. When I get back to the car and open the drivers side door, the alarm goes off;

3. Simulating this at home, it seems that opening either door, hatch or even triggering the bonnet alarm button will also trigger the alarm;

4. The car does have a remote/keyless entry system installed that works just fine (no problems in the time I have owned the car) and was installed by a PO (secondf owner or possible the first owner - I am 4th owner);

5. Alarm is easily deactivated by depressing the unlock button on the keyless entry FOB;

6. I have tried opening the drivers side door when the engine is running and the alarm does not trigger. Only seems to trigger when engine is off;

7. Also observed through some rudimentary testing that the alarm only triggers after a pre-determined time - seems to be around 15-20 secs (ish) i.e. if I park the car (engine off) exit the car, close the door then re-open with at least say 20 seconds the alarm does not trigger. if I wait a bit longer then the alarm triggers.

The problem has progressivelt been getting worse over the past 4-6 months and was initially observed to be occuring during hot weather and after extended periods in traffic i.e. car and engine very heat soaked;

Has also been happening during this winter but seems to ONLY be after extensive start/stop city traffic and/or suburban driving.

The car is not a daily driver and is typically used on weekends and during Porsche Club events and Landshark frenzy events.

At the moment it seems to be operating OK and the condition described above seems to have gone away after a recent Porsche Club Social drive day that covered some 300-400km of driving on rural roads.

My current thoughts are:

1. It appears to be thermal/heat related;
2. Are any of the alarm sensors gone "lazy"??
3. Do I have a heat related issue with the alarm electronics ECU??
4. BTW, where is the factory alarm ECU located in the MY89 S4s???
5. Could be a dodgy connector to the alarm ECU or to one of the alarm sensors???
6. Is the alarm triggered by current draw or resistance when say a door is opened???
7. Using the long key in the door does not seem to make any different versus using the keyless entry (which I use all the time of course);
8. All ground points were done within the last couple of years and I have checked voltage levels at battery, at charging point and all appears to be within specs - no engine start and engine start

So, where would the you suggest I start looking or suggestions as to possible cause.

Thanks in advance

Cheers