door locks bottons stopped fuctioning?

[Bob G]

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

[Peter Guenther]

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)

[Bob G]

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

[Peter Guenther]

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.

[Bob G]

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

[Uncle Acky]

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.

[Bob G]

Thanks uncle for your advice.

This is first positive answer to my question I received since my post I will try your anology and hope forthe best. I am trying to get my alarm person to disconnect theafter market alarm.

should I turn the ignition to the KOEO position to check the pump after I disconnect and reconnect the plug to the pump. I will print out your instructions and try this tomorrow. Also would you recomment replacing the fuses you mentioned to remove?

I will post if you suggestion worked wish me luck!!!

Sincerely
Bob Geco
1992 sportline 300E

[Uncle Acky]

You are welcome Bob.

The ignition does not have to be on if that's what you mean.

Make sure to at least remove the fuses to check them carefully, sometime there is a thin crack that is hard to detect but the fuse is bad even though it looks OK.

Power to the pump is from fuse C to a connector at the drivers footwell to the rectangular connector at the vacuum pump via the red and white striped wire. This wire must have 12 volts at all times.

The ground wire (brown) must be connected to ground.

There is another wire in the connector, possibly black and yellow stripe originating from fuse A which has 12 volts only with the engine on or cranking.

These must be checked with a volt meter.

First try to re-set the pump and make sure the fuses are good and it has power.

The system should work normally even with the remote system in place if it did before the problem happened, unless the remote unit or relays were damaged when the button became stuck.

I installed a remote entry in my car and it's nice to have for convenience.

Take care, and Good luck,
Acky

[Bob G]

What confuses me in your previous post is how to reset the vacuum pump under the left rear seat cushion. I took a look and there are at lease 3 large plugs with large looms of wire attached and a small 3 prong plug that goes to what I call the vacuum relay . It has a hose small hose attached to it and is easy to unplug the small three piece wire connector from this small item.

Can you send me a picture of which connector I should unplug. should this be done with the ignition in the number 2 position not running or with the key off. Reconnect the plugs and then try the lock to see if they work via the key in the driver's door lock or trunk lock?

I looked at your last post Uncle ! I may not of understood please clarify what you mean by resetting the pump?

you help is very much appreciated.

Sincerely
Bob Geco

[Uncle Acky]

I think you are looking at the Convenience control relay and the vacuum switch for the rear seat headrest (activated by the switch in the dash panel to drop the rear headrests down).

These are under the rear seat on the left side behind the drivers seat.

The vacuum pump unit is under the rear seat behind the front passenger seat.
lift the insulation, it is housed in a black or grey foam housing that splits in two pieces. Carefully remove the housing so as not to pull off the wiring and vacuum connections to the pump.

I will try to get a picture for you but for now look under the right side and the last post may make sense.

The key does not have to be in the ignition at all for this.

The red/white wire to pump has power all the time (key out or in any possition and engine running or not)

The black/yellow wire to the pump however requires that the key be on, engine running or cranking.

after you disconnect and reconnect the wire connectors at the pump, just try locking/unlocking the car with the key in front doors and trunk.

Let me know what you find, good luck with it
Acky

[Uncle Acky]

Bob, I tried to send you a pm private message but could not, you may have this feature disabled.

You may find the components of the remote entry system in this area near the pump, don't let this confuse you.

The pump has two electrical connections one rectangular (power and ground as described)

AND one round connector (these wires have either 12 volts Unlock or GROUND CONNECTION lock signal from either front doors and/or trunk lock) Also the vacuum lines go to the pump too.

On your w124 CD, go to disk 1, select model, select Electrical troubleshooting manual, select Wiring diagram, type in page number 143 in the PDF menu bar or go to page 143 see wiring of all door lock components. Follow the power wires in the diagram down to the (vacuum) Supply Pump, also follow the main red/white wire to the front door locks and trunk lock. You can clearly see how turning the key in the lock will send either 12 volts OR ground to the vac pump. You will note that the Anti theft alarm and convenience control unit are also part of this circuit but just follow the lock and unlock components.
Acky