I've been troubleshooting a random alarm trigger for six to nine months, and am now hoping for advice on anything I've failed to check or could replace.
First, what I've replaced: RCM, the alarm, door lock air pump and glove box light/switch. This has decreased the alarm triggering, so there were probably multiple faults originally.
I've checked inside the tailgate/boot lid area - I can't see signs of water ingress or corrosion.
The door contacts push in and out fine, but I guess could still be replaced (anyone know best replacement sources?). I don't know how to check the lock on the fuel cap or the tailgate catch.
I *think* I've identified that the only conditions most likely (but not consistently) to trigger the alarm are moisture in the air. After those equipment replacements, it now only triggers outside, in the late evening/early morning (sheesh), but not necessarily when its raining.
This suggests that it's an electric contact somewhere?
What are your thoughts?

 

I would try just unplugging the alarm siren. No one pays attention anyway.

 

That was a waste of time UNLESS you:
Tore out all the trim.
Dug down to the CLP/SSM.
Removed the CLP/SSM from it's insulative blanket (which traps moisture very effectively).
Looked the CLP/SSM over for water or corrosion.
Unplugged EVERY connector and looked at EVERY pin for corrosion/standing moisture.


I am not sure what you are saying, but if you are saying that you think moisture is the only condition to likely set off the alarm, you have the wrong idea.
The most common issue is corrosion on the alarm siren module caused by leaking batteries on the module's circuit board. Moisture in the CLP/SSM is a leading cause, but not the number 1 cause.
Moisture in the air is not a cause at all.

 

Just a thought.
Try pulling fuse #9 in the engine fuse box. See if the alarm still goes off overnight.
These fuses are old and sometimes the break but barely touch. I think it's he cooler temperature, not moisture, that may be causing the fuse element to make contact and set off the alarm.
Do your dome lights work? I believe they're connected to fuse #9 as well.

 

Thanks, and good suggestion. I didn't pull the fuse but replaced it, and alarm went off. Although not overnight - the alarm might not go off for two to three days, so you can imagine that trouble-shooting is darn slow!

I'll try pulling the fuse totally and see what happens, as the contact inside the slot might be 'iffy'.

 

Thanks Pizzaguy,

I have seen the considerable stuff on this forum about the alarm issue so I first checked the siren and replaced it with one from needs wings. The alarm still triggered - perhaps less often - and now it sounded crisp and loud, rather than the dying cricket.

I read a lot about the boot moisture issue so I did get down to the CLP/SSM and totally expected to see signs of moisture - like electrical corrosion - but didn't. The CLP was dying, as the locks took time to close, so as mentioned in my post I replaced the whole thing with this: https://www.needswings.com/central-locking-pump. All locks now close crisp and sharp.

I did not consciously check each connector for corrosion though, so I will do that - although its a darn pain to get back in there! I think I would have noticed corrosion in the connectors though.

How possible is it, do you think, that its a faulty actuators in the doors, fuel cap or trunk door?

 

That was my inclination, but my auto electrician pointed out that the lights will still flicker, and could drain the battery.

 

A lot of owners have had problems with the alarm batteries failing and leaking onto the circuit board and causing corrosion. Your problem could be caused by a failing alarm making it go off. Replace, unplug or remove.

 

Thank you - yes, I'd spotted that malfunction, so the siren has been completely replaced. I think it reduced the incidence of false triggering, but it appears more than fault was occurring. But at least the siren now sounds a lot better when it goes off!

 

Might a defective tow sensor cause alarm actuation? It would be rare but our cars are getting older.

The antitheft alarm is armed within approximately 10
seconds after locking the vehicle. A blinking light in the
tow away alarm switch indicates that the alarm is armed.
Once the alarm system has been armed, the exterior
vehicle lights will flash and an alarm will sound when a
door, the rear liftgate/decklid, the hood, or the glove
compartment is opened, or if someone attempts to raise
the vehicle for towing.

 

Good thought thanks. Where the heck is that tow sensor located?

It might be easiest for me to replace each related lock actuator and sensor.

 

I believe it is in the trunk. I will try researching it.

R/H side of the trunk area near the bulkhead. I have never seen a way to test it.

 

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A couple of times (many years ago) my car would alarm randomly (lights and siren) when parked & a visiting B-1 Bomber would fly in or out of the local AF base. Unless your in a high military/emi interference area I too would think it is a component of some type. Wish you luck!


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