HELP!!! disable factory alarm on 84 500sel!!
 

First time posting here and I just bought my car last weekend. I have used the search function and everything I have read tells me to look under the false plastic firewall in the passenger footwell and disconnect a cable from a box marked Becker Electronics or something like that. When I remove the plastic panel, there is nothing behind it, only the real firewall. Connected to the back of the plastic panel is a light gray box with one connector connected to it about 1.5 inches long. According to the label on this box, it has something to do with the built in car-phone and its connected transponder. I need to know where I can disable the alarm because it goes off 10 minutes after locking the door or if I try to unlock it via the passenger door. I found what looked like an aftermarket hood in the engine bay and a disconnected it but the factory alarm still went off. I need to disconnect this tonight so I can lock my car at school tomorrow without it going off.

I am also trying to figure out what my car came with since there was no instruction manual with the car. I also don't know if it is a Euro or US model. The temperature control is in Centigrade (Celsius).

Any help on either of these would be greatly appreciated as soon as you can respond.

Thanks.
Brett

Brett,

It sounds like an aftermarket alarm. There are too many varieties for anyone to help without being at your car. I hope my advice isn't too elementary. Trip the alarm and trace the sound to the siren. When you find the siren, disconnect the wires. Then go to a stereo shop and have them disable or remove it.

If it's a US car, it will have a VIN tag along the driver's windshield pilar visible from outside. The VIN should begin with WDBCA37A or something like that. If the VIN begins with WDB126037 or just 126037, it's not a US car. The numbers on the firewall behind the battery are NOT the VIN... at least not in the DOT sense.

Sixto
91 300SE
81 300SD

Sixto,
Maybe it changed in 10 years... but my C280's VIN starts with WDB....

:confused: :rolleyes: ;)

thanks
 

It is a US car because it stars wdbca37. I thin I used the wrong word in my previous post, I found and aftermarket horn, but disconnected it and I still have the alarm problem. I have traced the sound and it comes from one of the two factory horns attached to the radiator and I'm having the same problems as other have stated. If I lock the car via the driver door and try to unlock it via the passenger door, the alarm will go off and I have to go over to the driver door to disarm it. Are there any other locations for the alarm control? When I got the car it had an aftermarket stereo and I put a cd player in so I assume that's not the problem. I did notice when I had the console apart for the stereo, there was a box on the right hand side of the console (left side of passenger footwell that had 6 wires going to it with each wire having a number 1 through 6. is this the alarm box? If not, I guess I have to call a local service place or the dealer to find out where the alarm box is or how to disable it.

David,

Sorry for the confusion. Some gray market cars have a WDB prefix added to their chassis number to emulate the 17 character VIN. When the WDB prefix started in 80 or 81, the last 14 digits no longer took the form of aaabbbcdeeeeee where a = chassis designation, b = model, c = fuel type, d = transmission type, e = serial number. I could be wrong but it's something like that. FWIW, the 14 digit VIN didn't always match the chassis number either.

Brett,

The alarm controller I'm familiar with is where you're looking but it has two electrical connectors with about 12 pins each. I guess yours is different. It sounds to me as though some of the alarm switches that are part of your door locks are bad. There are two switches in each lock and it gets confusing when one of the two quits. In my case, only the driver's door has a working switch and only in the lock position. So I unlock the door, open the door and turn the key back to lock the door (which doesn't lock the car since the door is open).

Your situation is more complex because something's triggering the alarm. There might have been a wire to the radio that you didn't reconnect.

I'll check the manual again to see what's different between the 84 and 91 cars. I'm sorry I can't be of more help.

Sixto
91 300SE
81 300SD