2002 Jetta TDI- factory alarm going off randomly

So over the last few weeks, I've been awakened at night to the sound of my Jetta factory car alarm going off...it's happened about 4 or 5 times over the last 3 weeks or so. It's gotten to the point where I now disconnect the negative terminal at bedtime to avoid having to wake up the neighbours while I jump out of bed and race out to disconnect the battery. I've noticed lately (off and on) that when I park the car and lock the doors using the factory remote/key, sometimes the horn doesn't chirp like it's supposed to. This is also random. Didn't work the last two days but today it worked fine.

Am I getting some sort of a short in the alarm system or ??

This issue can be caused by the switch in one of the doors or the trunk becoming intermittent- this is known to happen with these cars.
Press the lock button and no beep = because one of the door switches (or trunk) is telling the alarm system the door is open, and the alarm won't arm when a door / trunk is open.
Waking you in middle of night because the switches were giving proper (closed) signal when the alarm was set, but the flaky switch is intermittently going to the "open" state. The alarm thinks a door/trunk is opened, and it screams.
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Not 100% sure because I have never had to service this (yet!!) on my car, but I think cleaning and / or replacing the door / trunk switches is pretty easy. Might want to search for that and service all of them as routine maintenance.
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Wish you all the best.

Thanks, sounds sensible to me. I'll look into how I can service the switches. Do you know where they are located on the doors?

Take a look at my sig, there is a link there for a door switch fix.

This particular problem might also be one or more pins in the door latch mechanism needing to be resoldered. Search for door latch fix - there's a great thread on it on VWVortex. I had this exact same problem on my 4-dr and resoldering the pins fixed it.

so i've narrowed it down to the hood. It's either the switch or a short in the wiring. I've been pulling the hood latch everytime I exit the car and haven't had an alarm go off since I've started doing this. Is there any easy way to replace the wiring that runs through the hood to the latch?

I'm having the same issue with my wife's Jetta. How would I go about isolating which door/trunk/hood is causing the problem?

Whenever I lock the car with the key fob, sometimes it honks, sometimes not.

TimShady said:

I'm having the same issue with my wife's Jetta. How would I go about isolating which door/trunk/hood is causing the problem?

Whenever I lock the car with the key fob, sometimes it honks, sometimes not.

Click to expand...

I just got lucky, I tried the hood first and the alarm still hasn't gone off on me. Now I just need someone to give me some advice on how I can isolate my issue to the switch or wiring...

problemjetta said:

so i've narrowed it down to the hood. It's either the switch or a short in the wiring. I've been pulling the hood latch everytime I exit the car and haven't had an alarm go off since I've started doing this. Is there any easy way to replace the wiring that runs through the hood to the latch?

Click to expand...

Anyone?

I bet you don't have to replace the whole wiring. Have you checked the connector right at the termination by the hood latch? It may have become dirty or corroded.

A work around that I found (although I understand you found one also) was to pull the fuses up under the dash on the driver's side (I believe they are S111 and S113 if I remember correctly from Bentley). It silenced the horn during the alarm sounding, while I find some spare time to tear down my car to figure out the short. The 2 fuses that I pulled are blue 15A fuses that are tucked way up behind the 10 and 6 pin connectors that run to the comfort module (not the conveniently located horn fuse on the triangular fuse panel) - you have to pull the kick panel under the dash to get to them easily.

I have a feeling that my issue is with my door solder joints, something that I will undertake over the winter.