benja

Hi there, I've got a really weird issue on my 89 964 C4.
A couple of weeks ago the horn started going off at random intervals every few seconds while the car was parked and locked. The neighbours hate me. I pulled the fuse, but it made no difference. And the steering wheel horn button no longer works.
I assumed it was a duff alarm, but the new alarm has been fitted, and its made no difference. Only way to stop it is to disconnect the battery. I tried driving it, but it keeps happening and everything thinks I've very angry....
Any suggestions what to do? Even just to stop it happening and silence the horn for good...?
Thanks in advance!

crg53

Does this happen when you park the car unlocked, or only when it's locked. If only when locked, your problem is in the light switches for the interior and/or the trunk and engine compartment. Try to disconnect them one at the time to find the culprit.

benja

It's when the car is locked, and unlocked and when I'm driving! No clear pattern either - sometimes loud beeps, sometimes quiet. Sometimes almost constant beeping, sometimes every 10 seconds.

I'm wondering if it's just the horn failing in a really odd way, or shorting somewhere. Is it possible to cut a cable to take the power away (removing the fuse hasn't done anything), rather than have to get under the wheelarch?

benja

So the chap fitting the alarm found the problem. The factory immobiliser circuit box had a load of rainwater in it and the circuit board was shorting out. All fixed now.
Thanks for the input crg53

crg53

I am no expert on these sort of things, but if removing the horn fuse didn't do anything, then I would guess it must be an after market alarm that is acting up.
Start with disconnecting the horn at the source, get under the right front wheel well, take out the liner and then pull the wires for the horn, not a big job. If you still get the noise, you know its something aftermarket.