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Astra G / MK4 2.2 Alarm randomly going off

5K views 7 replies 4 participants last post by  ST_Boy 
#1 ·
Hi there,

My mums '52 plate Astra 2.2 has recently been suffering with the alarm randomly going off. I've checked to make sure there isn't anything hanging inside the car that might be triggering the ultrasonic sensors and all looks good. After searching the forums I've found that it's probably the 'powersounder' unit that's gone faulty and that it can be fixed by unsealing and resoldering in a new battery but I'll probably just buy a new one from eBay or something.

One thing though, when her alarm goes off I notice there's two tones of siren - one sounds like her horn and the other sounds like what you'd expect a car alarm to sound like - as well as her indicators flashing. Would both types of siren going off still be caused by a faulty powersounder or am I looking at something else here?

many thanks :)
 
#4 ·
Have you hooked it up to a diagnostics machine to see if there is anything recorded for the cause of the alarm - not sure if the MK4 stores this for future reading but worth a go if you have an opcom or a mate with one.
 
#5 ·
When you press the RCL button once have a look at the LED on the hazard light switch. If it's flashing rapidly this indicates a fault - which I believe can be read with the correct equipment.

As a quick fix to stop the alarm going off at 2am try just pressing the button once to lock it - don't deadlock it.
 
#6 ·
Nah, I don't have an opcom unfortunately, haven't been to a garage for diagnostics as they're wanting an hours labor at the minimum..
As a quick fix to stop the alarm going off at 2am try just pressing the button once to lock it - don't deadlock it.
Nope, tried that, alarm still goes off! I'll check the RCL button - LED thing, cheers :)
 
#8 ·
Right then, so tonight I replaced the powersounder. Nice and easy job once I'd realised it's located in the passenger wheel arch and not the drivers side like I assumed! Locking the car still yielded a flashing red light so the powersounder wasn't at fault - damn... I tested the door pins, both had good continuity and triggered the interior light. The bonnet pin is easily detachable for testing with a multimeter and this was also working just fine. Lastly I tried depressing the boot pin while locking the car and observing the red LED - after some fiddling I notice that sometimes the LED will flash and others it'll stay solid for 10 seconds before extinguishing and then slowly flashing (presumably signalling that the alarm is active).

So now I'm thinking the pin is faulty. I took it apart, cleaned with a fibreglass pen and refitted and now the LED stays solid for 10s - no more flashing. I'm guessing problem solved, we'll see soon enough :)
 
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