Car alarm randomly going off

[funkyrobot]

Hello all. I have a 57 plate Mazda 3 Sport and it has developed an annoying problem. Every so often, the alarm goes off. I has happened quite a few times over the Christmas period and is driving me mad (and anyone else who happens to live near where I park the car).

It started a few months ago when it was parked on a street. I left the car for ten minues and came back to it with the alarm sounding. I thought something had tripped it so thought nothing of it.

Then over the last few weeks it has gone off in a petrol station (whilst i've been paying for my petrol), gone off whilst parked in a supermarket car park, and gone off whilst on my parent's drive on Christmas day about five times. The last one was the most bizarre as it went off each time I locked the car until I actually started the engine, let it idle for a bit, then shut it off and locked it.

It then seemed fine until this morning when I drove it down the street and parked outside out house to put some stuff in the boot. It went off again for no reason.

I'm now sat at work and can see it out of my window and (so far) it doesn't seem to have gone off. This is after a twenty minute drive into work though.

Does anybody have any ideas about what could be causing this? I'm going to give my Mazda dealer a call soon to get it checked out but I don't have any idea about what to look for with this. I have read up about bonnet sensors (hood sensors in America) playing up and causing issues over the pond, and have read up about corroded door sensors etc. However, the car is only 4 years old and is in pristine condition. Could it be the battery on the way out?

Also, does anybody know about how to lock the car without setting the alarm? If it continues to play up i'm just going to do this until it's fixed. I'm guessing that locking it via the key in the door lock simply locks the car without arming the alarm?

Thanks all.

[andy-xr]

I bought an M100 Elan around 3 years ago and that had a really sensitive alarm system on it. The first night after having it go off 3 times I was out on the drive in a dressing gown with a pair of scissors snipping the wire to the siren.

When I took it down to the local auto electrician he'd spotted a duff boot sensor and the interior sensors weren't stuck on properly. The boot sensor was just worn from weather and being rubbed - might be worth a look

[funkyrobot]

andy-xr said:

I bought an M100 Elan around 3 years ago and that had a really sensitive alarm system on it. The first night after having it go off 3 times I was out on the drive in a dressing gown with a pair of scissors snipping the wire to the siren.

When I took it down to the local auto electrician he'd spotted a duff boot sensor and the interior sensors weren't stuck on properly. The boot sensor was just worn from weather and being rubbed - might be worth a look

Ok, thanks.

Just called the dealership and it can't be looked at until 9th Jan!! So hopefully I can look for something in the meantime. They did say that you can lock the car and disable the sensors by pressing another button on the fob at the bottom. They also indicated that if the battery is starting to go that could cause it too.

Oh well, we'll see.

[Theflyer]

On my e46 it was the bonnet sensor.

[funkyrobot]

Theflyer said:

On my e46 it was the bonnet sensor.

Hmm. Bonnet sensor seems to be the problem in Canada too (where they seem to be a more popular car).

I think i'm going to contact the other dealers in the area and see if I can get it fitted in before 9th.

Would a dodgy sensor throw a fault code if someone checked the ECU?

Thanks.

[TooLateForAName]

funkyrobot said:

Hmm. Bonnet sensor seems to be the problem in Canada too (where they seem to be a more popular car).

I think i'm going to contact the other dealers in the area and see if I can get it fitted in before 9th.

Would a dodgy sensor throw a fault code if someone checked the ECU?

Thanks.

Probably not - the alarm is reacting to the sensor telling it there is movement/door open/etc.