Keyless entry problem - 1999 New Beetle

I've had a similar problem with a 2000 Jetta. I also sought help here, but nobody seemed to know anything, so I got the tools and dove in to the problem myself. I have a Bentley manual, and it is good for showing you how to get the doors apart and the lock mechanisms out, but it stops there. There is no real troubleshooting info. Here's what I've figured out so far.

My problem was twofold. Initially, I would just have problems with the driver and passenger doors either not fully unlocking, or unlocking but not registering as such with the computer ("Comfort Module"). Thus the doors would appear unlocked, and would sometimes open, but the alarm would go off as soon as you did, necessitating another press of the remote unlock button. This was annoying, but appeared to be mostly a mechanical problem with the passenger mechanism and the little switch in the driver's mechanism that registers the state of the lock button.

One day, suddenly and spontaneously, 3 of the 4 door locks just stopped working. Dead. The right-rear, gas tank, and trunk mechanisms continued to work flawlessly. The driver and passenger doors failing didn't surprise me, but the left-rear door did, as I had never had a problem with it. All I can figure is some sort of power surge, but the car was off at the time, so its only power was from the battery, and none of the "Comfort System" fuses were blown. (There are 2 hidden ones above the relay panel in addition to a couple on the standard fuse panel.)

Obviously this problem wasn't going to be resolved through cursory means, so I did some explorartory surgery on the driver's door, and with wiring diagram and meter in hand, cut into some of the driver's lock harness to check signals, "locking" and "unlocking" along the way. The signals were all what I expected, so the problem wasn't with the Comfort Module, but with the mechanisms themselves. I figured maybe an internal fuse in each one. I couldn't go any further though because I lacked the funky 12-point screwdriver needed to extricate the mechanism. The Internet provided me with this tool, although at more search effort than I expected. Armed with the proper tools, several weeks later I returned to the problem and removed the passenger side lock module and took it to my workbench (read "kitchen counter"). Using a 12v power supply, I applied power directly to the motor lines to see if it would operate. Nothing. Reverse polarity. Nothing. Time to take it apart. Many Torx screws later of at least

3 different sizes I had the module open. It consists of a small motor, a mechanical apparatus of several gears and a PC board with a single microswitch that detects the position of the mechanism. No other electronic components of any kind. The problem had to be the motor itself. I removed the motor and tried to power it. Still dead. Might be brushes. Take the motor apart. Pain in the ass. Brushes look okay. Tighten them up. Apply some contact cleaner. Reassemble. Apply power. ZOOM! Score! Remove power. Put back in mechanism. Apply power. Nothing. WTF? Move mechanism manually. Try again. CLICK! Worked. Hmmm. The motor is only starting from certain positions. Either there is a bad winding or the brushes are making intermittent contact. Either way the motor is trash. Given the unusually long shaft and the strange clutch mechanism bound to it, I won't be finding an off-the-shelf replacement. I'll have to replace the whole lock mechanism.

The VW dealer wanted $150 apiece for them, so I kept my eye on Ebay. All I was able to find were a RF door unit and 2 LR units. I got them all for about $180 with S&H. Fair deal. The plan was to use parts from the 2nd LR unit to refurb the LF unit. Left and Right parts can't be swapped because EVERYTHING is mirrored, even the rotation of the worm gears.

I first replaced the RF unit and once I got the exterior handle tension right it worked flawlessly. Second, I did the LF unit, combining the actuator from one of the LR units with the latch from the existing LF unit. This included the circuit board with the microswitches on it. Some slight Dremel modifications had to be made to the plastic case to make the lock cylinder fit, but I did get it to mate up. I installed it and it checked out okay.

I still have not installed the LR unit, as it involves a bit more work to get the door apart and working outside in Florida in summer is miserable.

About a week later a variant of the original problem with the LF door re-emerged. The door will often not lock, but will think it is locked, causing the aforementioned alarm problem. The "headlight warning" beep when the lights are still on and the driver's door is open also does not work. I suspect a faulty microswitch in the latch mechanism, which was never changed.

Long story a little less long, you have to swap out the lock modules. It's the only sure way to fix the problem. Chalk it up to yet another flakey VW electronic amenity. It is still a mystery to me how 3 out of 4 motors all failed at the exact same time.

...Sean.

Thanks Sean.

I also noticed that if I open the door after unsuccessful lock it will not trigger alarm - but alarm will go off if I try to start the engine. I guess the same like yours.

While searching door lock as you suggested I found this article. It might help somebody:

Now I need to find that door lock for driver side ...

Yes. I get that too. The alarm rearms because it thinks the door was never opened.

...Sean.