Hello W!

"I will assume that you bought the vehicle with this alarm, otherwise you would have returned it to the person who installed it, right? "

I bought the vehicle with the factory alarm (of course) but I had the external alarm installed after I bought it by an electrician, a very wise person who does alarms. He isn't MB qualified though.

"Also, after some searching, I see you 300D is a 1992, right? "

Correct.


" Because of the convenience feature, you need to wait at least 10 seconds (or maybe more depending what the timer relay is set to) between uses of the remote... otherwise crazy things happen like you are seeing. "

There is a time relay - after remotely locking the car the external alarm also activates the relay that holds the locking wires for 12 seconds. Then it releases the wires. Also, when unlocking the car the external alarm holds another 2 wires, simulating a key unlocking thus setting the factory alarm off. That for approx 2 seconds.

"My recommendation is disable the factory alarm. "

I thought of that but didn't know how to. Also I was afraid that with disabling the alarm the window feature would also get disabled.

" The factory alarm should have 2 plugs on it, a longer one and a shorter one."

Where are the plugs? I haven't actually searched for the central unit of the facotry alarm. What I fiddled with was the door switch for key - 3 wires and a plug underneath the passenger, right by the red airbag plug. I had that unplugged but the alarm still activated.

" Better would be to cut the factory alarm "ARM" wire which "should" be the yellow wire with blue stripe on the smaller plug. "

Where would I find that wire and that plug?

" Don't cut it there, as it will be hard to reconnect. I believe you can get to that wire from the passenger footwell along the door side. You'll need to carefully cut open the wire sheath. Also, the factory "DISARM" wire should be the green wire with blue stripe... should you need to cut that one as well (although I don't see why you would). "

Not a problem cutting it. I can always resolder and insulate it. I am afraid though that cutting the arm/disarm wires will result in having the window feature inoperative as well. Have you tested that? I remember that when I somehow disarmed the alarm tit didn't go off (good) but neither it closed the windows (not as good). Are the factory alarm and window closing 2 separate entities?

"Is there a red light on the dash that blinks when the alarm is on?"

No.

" I will probably disable the factory alarm the same way... so I await your findings. "

The electrician goes for a holiday this Friday for a fortnight, new findings in 2 weeks I am afraid. However I have a feeling that with the disabled alarm you lose the window feature. I will get back to it after he returns because I want to have it operational. Will keep posted.

P.S. Gave a call to local MB service. The guy said it would be no problem but I think he had no idea and said a general 'yes come over, we'll look at it'. If the electrician won't make it workable I will give the vehicle to MB.