1992 300E 38,000 miles. We got an alarm clicker not sure if factory or not. comming come from a long drive from San Degio my wife used the clicker to unlock the doors. Lights flashed and continued to flash like some one pushed the hazard switch, second the door lock buttons would not stop going up and down.

I asked my wife to pull over so I could prehaps reset the alarm turned off engine removed key from igniition. Problem stopped I alarmed the car again this time the door buttons stopped working and the parking lights starting flashing again.
finally got the flashers to stop. Pushed down drivers door booton noticed the fuction of the automatic door lock botton fuction stopped working. I pushed down manually on the drivers door button all the door lock botton had stopped fuctioning. I tried to see if they would work by using the key to lock the drivers door from out side, no change.
also tried the trunk lock no change.

Is their a fuse that could of overloaded in the main fuse box in the engine bay? Alarm works but door lock botton fuction inopt. very disappointed at this milage it would do this.
I took apart clicker to check botton fuction and battery one botton was pushed and stuck may have contributed to problem.


Were next do I check to trase down problem?

Sincerely
Bob Geco
M103

I think you are correct that someone has installed an aftermarket alarm, the MB version never had anything to do with flashing the lights. I think turning the door key activated the locking pump, and so did the factory remote. The factory remote was a switchblade kind of thing that you had to aim at the door handle sensor (at lest on my 92 S class)

Yes indeed after market alarm also good put. I lifted the rear bottom seat cushion out and inspected the vacuum hoses. all seem like new. I am wondering if the small relay box that the hoses and wire reciptal plug into might be bad? how do you test this? No blowen fuses in the engine compartment fuse tray? I only have a fluke 88 Multi digital meter. Do I unplug the this small box and measure the ohoms signal to a good ground what kind of reaading should I look for? does the key have to be in the first or second position?

Is their a relay some place else I am over looking?

If that the problem it is an easy fix. Please I could use some guidence. I went through the 300E CD under body and found the information but, it is very confusing to be. I need some one to help me break it down so I understand whatthe scamatics are saying?

I also do not have any fancy Mercedes-Benz equipment.

Bob Geco
1992 300E M103

I have never troubleshot one, the system works by either the remote or the key switch in door or trunk the key closes a microswitch which starts the pump providing pressure to the elements to unlock, to lock the key closes another microswitch which causes the pump to run in the other direction and produces vacuum to lock all the doors. This pump also provides pressure to lumbars, and vacuum if the engine is not producing any, and vacuum for the manual headrests. There are internal relays that control the flow of air to the various consumers and timers, 10 seconds for locking, 60 seconds for other consumers along with a pressure sensor. you should be able to hear it run. It could be brushes, it could be the internal circuits.

My hope from this forum is to gain a degree of knoledge as to were to start my investagation into this problem. all other systems seem to be working. I tried the recommended key in the trunk to see if it would get the door lock functioning no dice. I am preplexed at 38,000 miles how something like this could go out.

I am not trying to save a nickle by not handing my car over to a good Mercedes-Benz technician. That would be the last resort if I cannot fine how to fine the problem. My hope is that since I could not fine any DIY proceeders on this problem on this forum to ask for the forums help from one of the many master techs as to an educated proceeder to test which items might be the problem.

I appreciate the dialogue here but I would like the forums best and most experienced people to help guide me through this problem. I love this car and it saddens me that I feel helpless to try and attemp to cure the problem before I give up which is not a work I am use to using .

I hope the best and the brightest will answer my call .

Sincerely
Bob Geco
1992 300E M103 spotline

Hi there,



I suggest you carefully check (or replace) fuses 1, A, and C.

then get down to the vacuum pump again and unplug the two electrical connections to the pump - one rectangular 3 wire (power and ground) and the round 3 or 4 wire (controls/activates pump with positive or negative voltage to activate pump to lock or unlock).

Now re-connect the wire connections (I have read that this can re-set the pump after a fault of some kind)

Now try locking and unlocking the doors again.

The button sticking in your remote sent out a constant signal causing the pump to continue to operate and the lights to flash constantly. this is dificult to diagnose cause we don't know how the installer wired it to your certral locking system.

Check for 12 volts at two wires of rectangular plug and ground at the brown wire. Leave the rear seat out while you are checking to clearly see (hear) pump operation.

Reply with results and we will go from there.