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KirkF 08-03-2004 03:11 PM

1989 C4 Alarm Problems
I have a 1989 C4,

-For the last 18 months when I start the car, the alarm arms itself and the doors automatically lock. If you unlock the doors and open them the alarm will sound.
-If I leave the door open and start the car the alarm doesn't arm. So I have taught myself to always start the car and then close the door after 10 seconds.

-I have tested the system with locking the doors with the key and manually unlocking the system and it seems to work correctly in all other regards.
- If I pull fuse 24 for the wipers/washers all the problems with the alarm go away. It acts normally (except I have no wipers) until I replace the fuse.
-There are no other after market alarms in the car. (I have searched)

I have looked in the passenger side front hood hinge area but I can't find the alarm module anywhere.

1. Has anyone found this module? Where is it? Can you get it out? Any pictures?

2. What happens if you just remove it? Does the central locking system / etc still function correctly?


Rushjob 08-03-2004 04:16 PM

You mention the passenger side hinge your car right hand drive?
The reason I ask is that the alarm module on my car is indeed behind the passenger side hinge, but it's a UK rhd car.
Check out the drivers side if you're's a black box about 2" by 3" by1" thick clipped to the bulkhead ( firewall ) at the back of the luggage compartment and a right sod to reach.

Computamedic 08-03-2004 06:29 PM


I've got an '89 C4 LHD Coupe and I believe the factory alarm unit IS on the passenger (i.e. RH) side behind the hood hinge. It's really set back a long way with the connector pointing away from you (i.e. towards the back of the car). I believe the wiring loom is long enough to allow the unit to be pulled out but I have to admit that I've never been successful at getting it out!!!

The alarm is set by the door switches which also activate the locking mechanism so it may be that if you remove the alarm you may still have the locking problem.

The fact that fuse 24 affects the problem would indicate some wiring issues since the alarm has an internal fuse and is not fed via any fuse in the central electric. Also fuse 24 must be ignition sourced (wipers only work with ignition on) so it could indicate a problem in the ignition switch area too.

I suspect that by removing the alarm you may be removing the effect rather than the cause.

Hope that helps,

Best regards


KirkF 08-04-2004 01:17 AM

Ok I managed to find the alarm. It is indeed buried on the right hand side.
Removing the alarm resulted in:
1. Car wont start (probably because it is no longer powering the DME relay)
2. Doors still lock 10 seconds after ignition is turned on.

I have run out of time to work on this until the weekend, but I am going to dig deeper under the dash and look for hidden after market alarms still tucked under there somewhere.

This problem looks exactly like an aftermarket alarm auto locking the doors. I have pulled a bushel of bad wiring from other poorly installed devices in this car, so perhaps I have missed one of them. I will search around the central locking unit / keyswitch to see if I can find any more foreign pieces tucked in there.

Someon may have used Fuse 24 for their power since it is ignition power and available under the dash.

(I removed handfuls of bad stereo wiring, and one after market alarm, and what looks to be pieces from a second aftermarket alarm so far. Maybe the main box is still tucked in there somewhere tied into things.)

I have also traced the alarm wiring in red through all the schematics so I should be able to look at whats happening on all the alarms input signals.

Basically the 'Control Unit Alarm System' is wired as follows:
(pin names are almost unreadable on my schematic but here is my best guess)

87c bk/br DME relay
t- br/wt Door contact switches / interior lights
A br/gn Door unlock contact
E br/bl Door lock contact
mk br/rd Radio theft contact
br/rd Luggage open contact
31 br Turn signals?
15 bk power (15)
87 re abs control unit??? starter/generator??
30 power (30)
hk re/wt warning flasher
re/wt alarm horn


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