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1993(K) Alarm/Interior Light Issue

SterlingMess

SterlingMess

PCGB Member
Member
I've read many threads on other forums relating to the 964's alarm and interior lights, many overlap, but I can't find anyone who has had exactly the same issue as me.

In a nutshell- my interior lights won't go off when the doors are shut.

If I remove the bulb in the boot and switch off both interior lights, I can set the alarm correctly from the door key (rapid LED flashing for 10 seconds, then a steady 1 second).

If I put the bulb back in the boot and switch both interior lights to "door" function, I can set the alarm, but the interior lights (and boot light) do not go off with both doors closed. After 20 seconds or so, I can hear a relay click in the alarm control unit under the driver's seat, but the interior lights stay on. (This is why I have to remove the boot bulb and switch off interior lights.)

I have buzzed out the boot micro switch by the latch (it doesn't have a switch by the strut) all is okay. Again, when I activate the micro switch with a tool, I hear a relay clicking inside the car.

Do I need a new alarm control unit? Or have I missed another step? (I don't yet have access to an OBD reader to check fault codes.)

BTW, my engine cover light works okay with its microswitch by the latch, and so does my glovebox light.

Other clues:

A previous owner fitted an engine immobiliser which requires the presence of a fob near the ignition key.
Another previous owner fitted the Porsche Classic Radio Navigation radio (which I am about to replace for a Blaupunkt Bremen with DAB and Bluetooth).

Thanks in advance for any suggestions.
 
SELF FIXED

I'm embarrassed to report that the issue is fixed, or rather, it never existed at all!

Stopped in traffic today, I thought I'd fiddle with the passenger courtesy light and noticed it didn't come on in the "door" position, whereas it was on permanently in the "door" position in the garage.

When I later stopped for petrol and opened the door, the light came on and went off as soon as I locked the door, and when I came back from paying, it went off as soon as I switched on the ignition.

I'm sure I tested some of these scenarios in the garage, and perhaps it required a start and drive cycle (speedometer input to the ACU?) to reset.

Next job...
 
Job done then! Never really think about mine - they're always in the off position avoiding any chance of 30-year old battery drain gremlins that might show up one day.
 
That's what I'll end up doing, but on the other hand, there's something cool about 30-year-old electronics still working!
I did speak too soon because my set-up only works with no bulb in the boot. The courtesy lights never go out if I put a bulb in the boot. With no bulb (which I can live with), everything works just so.
 
SterlingMess said:
The courtesy lights never go out if I put a bulb in the boot.
Click to expand...


Regardless of the switch position? Time to go through the wiring diagrams for all those switches :)
 
Found it! The boot/luggage compartment bulb has a permanent 12V (so do the interior lights). Depending on the circumstances, it gets its (switched) ground from the ACU, but the ground connector shield by the bulb was a little worn and touched the inside of the boot itself! Hence the reason it was always on.
 
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