Volkswagen Golf III anti-theft alarm

Hello People:

Good news.. My car is back to normal now.. She does not scream anymore.. Yup.. She just needed 2 hours of my personal attention and is fine as always.. :)

I found that there is very little information available online to fix these problems and I am going to post my experience here so that it is useful for others who experience the same problem.

Looks like the anti-theft alarm, centralized locking, and the water drain system are always an issue for Volkswagen automobiles. My car is a 1995 model, volkswagen golf, with centralized locking and anti-theft alarm. The alarm is engaged when you lock the car and turn the key twice (your centralized lock should also engage with this). The alarm goes on everytime you open the car without using the key. To open all the doors you just turn the key twice. In my case both of this was not working and the alarm would engage if I try to open the door (even though the door opens). It makes loud, annoying noise and also stalls your engine. Hence, you cannot start the car. However, the annoying sound will go off in 1 minute, just to save the battery. The engine stall remains active and the alarm will fire again for 1 minute if you try to start the car or open the doors again.

The alarm control unit is located under the steering on the left hand side corner (near the air ventilation system). This gets input from all the doors, trunk, and the automatic opening circuit. It controls the ignition and the alarm horn. There are mechanically operated switches in the driver and passenger side front doors that will disable the alarm when you open the cars using the key.

Before doing anything, open your hood and disconnect the battery negative (the black wire). This will shut off all the power. [Note that your radio will be reset and you need a code to unlock it when you power the vehicle back. You can find how to unlock this in your manual. If you do not know your code, you can get it from your dealer.]

There are several potential causes for the failure. The important ones being:
1) The door switche (due to wear-and-tear) failure
2) The centralized lock / unlock unit (its poor location and susceptabilty for water flooding)

If you drains are clogged or the vapor seal is broken, the centralized lock / unlock unit in the trunk might get water in it when it rains. If the water enters the circuit board, it is a disaster. This indeed was the problem in my case and I found it as I was checking it. You can disconnect this module for testing the swtiches.

To diagnise the source of this problem, you also need access to the alarm control module. However, the access to this module extremely complicated in this model of the car. I was totally annoyed. Basically, if you remove the bottom trim under the driver seat, you will be astonished to see a hard metallic casing covering all the circuits. There are beams running across and the several control modules are mounted in the beam. This particular alarm control module is buried deep inside this metallis mess. Ideally, if you want to reach this in a clean way, you need to remove the steering, front air bags (gotta be careful with this as you can potentially blow this on your face while opening), and then the metallic cover. If you go to a service center, they might probably do this. However, I did not follow this as it is very time consuming and very tedious. First get a clear view of the alarm control module. It is located on the left side of the car behind the metallic bars (Hint: There is a opening on the door where all the wires are routed from outside. The module is about 6-7 inches above that almost near that).

The module have two connectors connected to it and this will be helpful in locating the module. A 10 pin connector and a 6 pin connector. All the inputs from the door goes to the 10 pin connector. If you have a small hand, you will be able to reach up to the connector and disconnect it without removing the metallic cover. Once you have the connectors unplugged, you should be able to verify if your mechanical switches are functioning using a multimeter and the circuit diagram (available from the service manual).

Good Luck!!!!!

PS: I am just posting my half-baked post due to lack of time.