Alarm goes off every time I lock my car

CaptainUnlikely · 25 Sep 2012 at 15:06

This issue started yesterday, I was driving back from Wales, stopped at a service station, all was well. I got back to Derby, pulled up and locked the car with the fob, and the alarm immediately went off. I checked all the doors and windows, and the boot, then locked it again, but the alarm came on straight away once more. Locked with the key and all was well.
I got home and this time even locking with the key caused the alarm to go off right away. I disconnected the car battery for an hour and reconnected it, after resynching my fob it locked fine. Got to work this morning and the key and fob both cause the alarm to go off.
The car starts fine with either my normal key or my spare, all doors lock and unlock fine, but the alarm goes off every time it's locked. If I hit the lock button again it silences the alarm, which is ok for the time being, but I'd like to get to the bottom of the problem. I called out my breakdown service just to see what they would say, and they suggested it's probably a switch in one of the doors that's causing it. I was just wondering if anyone here had any other suggestions.
The car is a mk1 MG ZS (51 plate), I'll post on an MG/Rover forum later but figured I'd ask here first.

leigh_boy · 25 Sep 2012 at 15:16

I know in my car ( not an MG) if i put coins or anything metal above the alarm modules it causes it to go off randomly, 1 modual is underneath the ashtray, ( i use it for coins) and the other is under the arm rest use it for all sorts of crap and coins)

bledd · 25 Sep 2012 at 15:21

This guy fits a lot of alarms, top bloke

http://sns.mike-graham.co.uk/contact.htm

Craigus · 25 Sep 2012 at 15:30

Do you have internal motion sensors? One of the most common things to go dodgy. Either disconnect them from your alarm module if you know where it is or failing that put some gaffa tape over them and see if it goes off.

If that fails, the door, boot or bonnet catches often can be the culprits, basically a little resistor that knows if a door is open and will trigger the alarm. Check these aren't bent.

HTH.

CaptainUnlikely · 25 Sep 2012 at 17:19

Craigus said:
Do you have internal motion sensors? One of the most common things to go dodgy. Either disconnect them from your alarm module if you know where it is or failing that put some gaffa tape over them and see if it goes off.

If that fails, the door, boot or bonnet catches often can be the culprits, basically a little resistor that knows if a door is open and will trigger the alarm. Check these aren't bent.

HTH.

I do, but they're deactivated when the car is locked with the key rather than the fob - I can confirm this as I have to lock it with the key if I leave the window open, otherwise the slightest breeze sets them off.
I'll have a good look at the door, bonnet and boot catches when it's not raining, and see if anything looks off. It would be a little odd if it was a bent resistor or something like that as it's not like any of the doors were slammed prior to this starting, but it's definitely something to check, thanks.