Alarm problem please help..

[trisaudi]

Our alarm has started to go off at night for no problem. It has been doing it for months now on and off. We have to dis-connect the battery at night now so we don't keep the street up. Its completely random times and often when there is no wind or any reason for it to go off!

Its an 1998 Audi A4 1.9 Tdi.. Not sure if there is a common fault. I even disconnected the fuse for the horn to stop it but it still went off! Alarm fuse and guess what... Really ****** off with it now and just want to sleep well again. Has anyone else had this snag?

I await some advice. Thanks in advance anyone who can offer some ideas


Tris.

[trisaudi]

Just found this searching:

My A4 alarm is in the boot right hand side behind the side trim in a well below the light cluster.
A quick way to determine whether it is the siren battery at fault is to take it out and measure the dc voltage between two of the terminals. Just keep trying two terminals until you get a dc voltage value. Mines was 6.8V - knackered. To remove the siren/battery unit you have to remove some trim. It is not a difficult job and if you want Audi pics and instructions then please PM me with your email address and i will oblige. Someone else on another forum followed the same advice and found the dc voltage to be less than 1V!!!!!!!!!
In both cases a new siren/battery unit solved the nuisance problem. £82 inc vat.

Is this in the manual how to remove the interior to find the spare battery, I suspect this could be the issue.. Why are they so expensive too what battery is it??!!

[kahuna]

Hi there.

Had the same problem with my A4 at the start of the year. Went through the same procedure of ripping off trim and cutting open the siren etc... Still had the problem though!

Eventually found the problem was the bonnet switch. I just disconnected it and hey presto no more 3am wake up calls from a lonely car!!

[olds_kool]

tris your 98 wont have a battery back type siren, it will have the earlier horn so thats not your fault
id go with one of the switches being faulty
or the interior sensors, try unplugging control unit under rear bench see if that stops it

[trisaudi]

tris your 98 wont have a battery back type siren, it will have the earlier horn so thats not your fault
id go with one of the switches being faulty
or the interior sensors, try unplugging control unit under rear bench see if that stops it

Thanks for the reply's guys. Saves me looking for a battery that doesn't exist. Where is the control unit under the bench? IS it obvious what it looks like?

[olds_kool]

on a 98 it should be the only electrical item under rear seat, middle front, bench just pulls out

[trisaudi]

on a 98 it should be the only electrical item under rear seat, middle front, bench just pulls out

Bit of a late reply I apolagise for that fella's its been an internittant problem all along so I havent really dealt with this still!

I did-connected the bonnet switch a few days ago and thought it was all sorted but it has since gone off again. I will pop out in a moment to locate this control box? Will update the post with results.

Tris.

[trisaudi]

Found the control box and its now dis-connected awaiting results now. Fingers crossed thats the end of that problem.

[chris_r]

Hi there.

Had the same problem with my A4 at the start of the year. Went through the same procedure of ripping off trim and cutting open the siren etc... Still had the problem though!

Eventually found the problem was the bonnet switch. I just disconnected it and hey presto no more 3am wake up calls from a lonely car!!

I've just replaced my bonnet switch as one of the terminals had corroded and snapped. The part was pennies from Audi and took seconds to fix. You can test it with a multimeter. If you have continuity when the switch is depressed it needs replacing.

This may help...

Multimeter Continuity Tutuorial

[trisaudi]

No problems since dis-connecting the control box. May check the bonnet switch over shortly though just to find out the cause. Im pretty sure the neighbours are alot happier now though