O.K., point taken--the situation was that while I could still lock / unlock the car as normal and the central locking system functioned fine, it was the alarm system that didn't. The alarm (when the car was in its previous state) would only arm / disarm correctly from the tailgate lock, which, of course, has no differentiation between left and right. The driver's side (US left) would neither arm nor disarm the alarm when the car was locked or unlocked. However, if the alarm was set off, then it would shut the alarm off if the key was turned in the cylinder. On the pass side, unlocking the door would arm the alarm and locking it would disarm. When this was the case I had a few options. I could just not have the alarm activated and lock and unlock the car from the driver's side. This is primarily what happened until someone ripped a chrome piece of the car and I decided the alarm might add some deterence. Or I could lock / unlock from the tailgate, and everything, including the alarm, would function as prescribed. Of course, I could not use the pass lock at all, because every time I unlocked the car from there the dumb alarm would go off. So when one of the locks was sticking, I just switched the whole lock cylinders in the front door, and---voila! Now the alarm works perfectly. However, the convenience system doesn't work at all. I will do your test to see if the problem is in the lock cylinder or the actual relay module. One clue to the problem is that if I attemtp to operate the rear windows in the car with the key off and both doors closed (or opened) and from the rear switches, I can hear a clicking coming from the unit under the rear seat. So I assume this is the problem.
Sorry for being so long winded.
By the way--just curious to see if American legislation changed any of the options...

On the american model, when the alarm is set off, do the headlights and taillights flash and the horn honks, or is it the parking lights and horn?

On mine I can operate the sunroof, seats, radio, power steering wheel, and all windows without the key in as long as one of the front doors are open. (At least I am supposed to be able to...)

Does the American model operate in the same way?
Thanks

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2002 Mercedes-Benz E320 4Matic
1995 Mercedes-Benz E320 Wagon
2005 Land Rover LR3 V8 SE
1999 Audi A8 4.2L quattro