Robert Coats

Maybe it's the cold weather, but my alarm is going off at random times, usually within 1-10 minutes after I park and lock the car. I don't believe the alarm is much of a deterent, so I'd simply like to disable it.

How?

Is there perhaps a single fuse I can pull?

Will disabling the alarm cause any problems?

Thanks as usual, folks, for your sage advice.

Adrian

Dear Robert,
To disable the alarm is a bit of a pain. The alarm unit itself is tucked up right at the rear of the trunk under the LH hinge (looking from the front). The fuse for the alarm is mounted on this unit inbetween the two microconnectors. You cannot see any of this of course.
Now the most common cause of this alarm problem is the glove box switch. I would suggest that either something is interferring with this switch or it is loose or out of adjustment. Maybe even a sagging dash.
Most likely one of the alarm inputs is changing state and this sets it off. These inputs are,
Door switches (X2)
Trunk switch
Engine lid switch
Glove Box switch
Radio rack switch
Rear cover switch (Cab and Targa only)
There are a few more but these are the most common, known to fail,
Ciao,
Adrian
911C4

964Cab

Adrian:

Where is that, "Rear cover switch (Cab and Targa only) ?

Thanks,

Patrick

Robert Coats

If this is true, shouldn't the alarm go off right after being armed?

Or, is there some kind of delay (how long?) before the alarm actually becomes active and detects the switches is not open/closed?

My alarm goes off 1-10 minutes after locking the doors, but not every time.

If I do manage to find the fuse for the alarm, can I just pull it to disable the alarm? Will there be any other problems if I do this?

As usual, thanks for your help sir.

Adrian

Dear Robert,
The alarm works on changing state inputs. From an earth to open as an example or vice versa. This can take time to happen physically. As something cools the metal contracts and eventually breaks contact. I know with the glove box switch is was the thickness of a gasket which made the difference. As things settle out after a good drive a badly adjusted switch makes or breaks contact. Not uncommon with the rear spoiler I might add. The pure action of locking the doors. Sometimes a full earth is made under the actuators maybe sometimes not and this becomes open. Hard to say but all the above happen all the time.
One thing you can do is get your wife to lock you inside the 964 and start thumping things around a bit. Gently of course (technical taps), see if you can set the alarm off from inside.
I would certainly be checking to see if the trunk light is "off" when you walk away and if the alarm is then set off, see if this light is now "on". You can see through the front grill, do not open the 964 or open the trunk. You need to check that these switches are playing up in their closed positions. Maybe you have moisture dripping down onto one of these switches providing an earth or open signal change of state.
You can use the Bosch Hammer and the special adpaters to check this system but you need access to the alarm unit.
Removal of the fuse for the alarm will have no effect on anything else in 964.
The rear cover switch is under the right hand side of the cover, I think. I am sure it will be easily found,
Ciao,
Adrian
911C4

Rich W

Robert,

I had a very similar problem with my car a number of years ago. Turns out the climate control unit had gone bad and the sampling fan was running continuously. The alarm system read this as an amperage draw on the system and triggered. The problem stopped when the climate control unit was replaced.

MikeF

Through all that I believe Adrian confirmed that it is OK to simply remove the fuse. Additionally, the horn for the alarm is located immediately behind your passenger side headlight. You can access it by removing the front passenger wheel and removing the mudguard. Look up and you will see the two horns actuated by your horn button, and then look forward and you will see one flat horn by itself. Seems reasonable to simply unplug the leads from that horn.

Either way, no more horn. When the weather warms a bit and you have a spare afternoon, have Maria lock you in the car as Adrian suggests and tap away. Be careful though, she may not let you back out.

Happy new year!

speedster 94

hallo
Depending on the year you will not have a switch on the Engine and Trunklids but a contact in the Hoodlocks ,easy to check. If you have a wire on the lower Locks then they are the newer ones and you dont have a extra
switch. This is for the Lights and for the Alarm. On Euro Cars from up 92, I am not sure from when on US cars.
Harald

mjshira

can anyone tell me which fuse if for the alarm? I would like to remove the alarm system....