Hi, My factory alarm in, TH auto Wagon 140k, has started to go off for no apparent reason. Usually about 10 minutes after parking. When I use the remote to unlock the car I get two short beeps and have to press again to unlock. Sometimes it goes off again after 10/15 minutes.

Is this common?

Any clues?

Thanks

While we're on the subject of alarms. My under bonnet siren has died. I've bought a replacement generic unit from Dick Smith. Any tips for changing it over (like wear ear muffs or something)?

[QUOTE=Ian]Hi, My factory alarm in, TH auto Wagon 140k, has started to go off for no apparent reason. Usually about 10 minutes after parking. When I use the remote to unlock the car I get two short beeps and have to press again to unlock. Sometimes it goes off again after 10/15 minutes.

Is this common?

Any clues?

Check the voltage of your backup battery, If it's getting low that will set the alarm off

I assume the optional factory alarm uses the horns as the siren?

might be a faulty door switch, or bonnet switch causing the alarm to go off.. 2 beeps meaning " something is open ".. in my experiences.. ive seen the bonnet switches play up.. pop the bonnet, and bend the braket that holds the switch upwards.. to make a good contact with the bonnet when it shuts! hope this helps! there is a procedure to get codes from magna alarms.. using the highbeam lights, flash them a certain amount of times, and see how many times the " security " light flashes.. count the flashes, and it will tell u if it detects a fault in a switch, etc

I know its not on a magna but in my old car I had the exact same problem.. It too ended up being a dodgy bonnet switch that just needed to be replaced.... It too wasnt a factory alarm but the principle of the matter remains the same

Id say faulty switch too. im having same prob, see if the interior light is on cause if it is it things a door is open then thats ur answer, faulty door switch

The factory alarm does not have a backup battery, and yes it uses separate horns as a siren. As aforementioned, it is likely the door or bonnet pin switches, the boot latch sense, or BCM. Quickest way to troubleshoot is with a Dealer scan tool as otherwise you are working blind.

Or you could always try a process of elimination such as disconnecting each of the trigger switches until the issue goes away, and then you know which switch to replace. If all switches are disconnected and alarm still goes off, you know it's a faulty BCM as a shorting wire would trigger the alarm almost immediately.

might be a faulty door switch, or bonnet switch causing the alarm to go off.. 2 beeps meaning " something is open ".. in my experiences.. ive seen the bonnet switches play up.. pop the bonnet, and bend the braket that holds the switch upwards.. to make a good contact with the bonnet when it shuts! hope this helps! there is a procedure to get codes from magna alarms.. using the highbeam lights, flash them a certain amount of times, and see how many times the " security " light flashes.. count the flashes, and it will tell u if it detects a fault in a switch, etc


Thanks for your help. It appears that the bonnet switch was the problem. I bent it up a bit and no problems for the past few days. As it happend after driving and then parking I was wondering if the "heat soak" was enough to move it out of tollerance.

Thanks again.