Door locks 1982 300SD W126 - PeachParts Mercedes-Benz Forum

sclancy · #1 04-10-2006, 05:03 PM

General question. My drivers door always locks all the door, but doesn't always open all door. (Passengers side front door lock and unlocks all doors w/o fail.) Has anyone seen this?

-Stephen
82 300SD

DrewGerhan · #2 04-10-2006, 07:54 PM

i just went out to try my locks. the driver door opens itself and the passanger side. i hear something pumping in the back like the 2 rear doors want to open but they dont. i locked the drivers door and the passanger and drivers rear both locked. i didnt manually unlock the passanger rear but i assume it would do the same. any one know what could be causing the rears not to unlock automatically?

Admiral Ahani · #3 04-10-2006, 10:46 PM

YoungBenz: Obviously there is a vacuum leak somewhere. Do you have a Mitivac? You need to find out if your system can store vacuum over night, or if the leak is constant. It sounds like the rubber nipple on the rear door lock actuators have torn, and they allow air to escape as they flex (when they are opening or closing). If you don't know what I'm talking about, open up one of your doors and remove one of the lock actuators. I don't know where to get those nipples besides from a dealer, so I just delete a vacuum lock actuator once it needs a new nipple. Once they're all deleted, I'll install electric locks!

sclancy: the driver and passenger lock actuators, which control the lock/unlock of the car's system, have one tube for lock and one tube for unlock. Maybe the lock tube on your front driver lock actuator is disconnected or cracked or something?

rhodes2010 · #4 04-11-2006, 05:20 AM

My 300SD just got fixed for a similar situation.
After locking drivers door, electric pump in trunk comes on,
other three doors struggled to lock.
I experimented with quickly (while pump was running) pushing
down or pulling up on the other three door locks.
They moved very easily, which told me vacuum was present.

When I manually pulled or pushed the passenger door the two rear immediately
followed up or down.
Only the drivers door is mechanical, the other three are vacuum.
Admiral: my 300sd has single vacuum port on door lock actuator,
the 80 and 81 300D have dual port actuator.

What to do: Admiral is right that it is a door actuator. Take the door panels
off, unplug vacuum line from actuator (you can do it without unbolting anything - except the door panel). I plugged mine with golf tees while testing.
If you isolate the bad unit, the rest of the system should work.
After finding the bad one, it is easy to drop it out of the door and replace.
Will not cost very much for a new one (from Fastlane).

In my case that passenger door was the only bad one, replaced it and
I have working locks again. In my 300D it was the trunk actuator.
Replaced it, and all my locks work again.

One more note: I used a 300D dual port actuator to replace my 300SD single port
door actuator. You can search for this W123 into W126 post.
Have to use the correct port to push/pull and it worked.

MercFan · #5 07-12-2006, 03:48 PM

My doors always lock and always unlock but they are SLOW (1-3): is this an indication of a mechanical issue that could be fixed by servicing/greasing the internal components or does it sound like it's a vacuum issue.

To my knowledge I don't have any other vaccum system-related issues since the tranny shifts smoothly, the car shuts off quickly, fuel door locks/unlocks perfectly, etc.

Please let me know -
James

dougand3 · #6 05-23-2008, 09:13 AM

Very nice narratives - Rhodes and Admiral. Just had this issue on 83 300SD - 3 nondriver doors lock/unlock slowly, then not at all. Your hints saved me time - cycle the driver lock and look/feel/listen for which ones TRY to work. On mine, the Front pass lock was totally dead - only one door panel to pull.

Found a brake bleeder/vacuum pump kit at Harbor Freight Tools for $18. Seems to work ok....at least for awhile...LOL

vstech · #7 05-23-2008, 10:10 AM

Just to clarify for you guys... the SD is not connected to the engine/climate control vacuum at all... it runs off a pump in the trunk. the drivers door switch is electrical and controls the pump itself. if yours are locking, but not unlocking, you could have several issues. pump, tubing, actuators etc...

bgkast · #8 08-12-2008, 02:34 PM

Quote:

Originally Posted by vstech

Just to clarify for you guys... the SD is not connected to the engine/climate control vacuum at all... it runs off a pump in the trunk. the drivers door switch is electrical and controls the pump itself. if yours are locking, but not unlocking, you could have several issues. pump, tubing, actuators etc...

So when you unlock the driver's door the pump should turn on and unlock the other doors? When I unlock my driver's door nothing happens but the driver's door unlocking, no pump sound or anything. Locking from the driver's door does not work either.

I’m still learning the W126 systems, some are quite different from the W123.

Phil · #9 08-12-2008, 04:19 PM

There seem to be a lot of door lock posts right now. My experience is only on a 1983 300SD but here is what I have found out.

1) The only key switch ,on mine, is on the drivers door only.
2) There are 2 wires from the switch to the pump in the trunk and depending on whether
you are locking or unlocking your doors the power will go to one wire or the other.
3) The pump in the trunk will either produce a vacuum (locking the doors) or pressure
(unlocking the doors)
4) Fuse 13 feeds the door lock circuit and there is a black/red wire from the fuse to the
door switch and then a blue wire and a yellow wire going from the switch to the pump.
The pump also has a brown ground wire.
5) The hose from the pump goes to a X fitting on the right side of the trunk and from
there one line to the trunk lock, one line to the fuel door lock and the other line goes
to another X fitting that is in a channel under the floor carpet in the front passenger
side. At this X fitting one line goes back and under the front seats to the drivers
side B pillar and then to the drivers side rear door lock, one line goes back to the
passenger side B pillar and then to that rear door lock and the last line goes forward to
the kick panel on the passenger side and into that front door and then the lock.
6) There is no vac/pressure line going to the driver’s door.
7) When the drivers door is open you can not press or pull the door lock knob, it won’t
move against the pressure/ vac.
8) The wires going into any of the doors are 20+ years old and can only bend back and
forth so many times before they break. When the wire breaks it some times only
separates inside the insulation so you can’t see it but you can usually feel it or find it
with a continuity tester.

I have never had to replace any of the tube/line or any of the fittings but I have had to splice in wire sections to almost all the wires for the locks, window and seat at the drivers door hinge area.

Last weekend the pump in my car stopped pumping although the motor still runs so if anyone has a pump they want to sell let me know.

bgkast · #10 08-12-2008, 07:13 PM

Thanks. That is quite helpful. The only part that confuses me is:

Quote:

Originally Posted by Phil

6) There is no vac/pressure line going to the driver’s door.
7) When the drivers door is open you can not press or pull the[Driver's?] door lock knob, it won’t
move against the pressure/ vac.

There is no vacuum lines or vacuum element in the W126 driver's door, correct?

Phil · #11 08-12-2008, 08:30 PM

Quote:

Originally Posted by bgkast

Thanks. That is quite helpful. The only part that confuses me is:

There is no vacuum lines or vacuum element in the W126 driver's door, correct?

Actually there is a vacuum element in the drivers door but it is not connected to any vac/pressure lines and is only there, as far as I can tell, to hold the button and it has the electrical switch in it. If you look at the picture I posted it shows the element that came out of my drivers door and you can see the connections.

bgkast · #12 08-13-2008, 01:58 AM

I worked forward from the trunk with my mity-vac and found that my front passenger door has a leaky element. I also discovered that if the system has a leak the pump will "time out" and not work until it has been reset by disconnecting the battery or pulling fuse 13. That is why it was not coming on when I locked and unlocked the driver's door. Once I plugged the line to the passenger door and reset the pump all the other locks now work with the driver's door.

Phil · #13 08-13-2008, 11:13 AM

This version has some additional info.

There seem to be a lot of door lock posts right now. My experience is only on a 1983 300SD but here is what I have found out.

1) The only key switch ,on mine, is on the drivers door only.

2) There are 2 wires from the switch to the pump in the trunk and depending on whether
you are locking or unlocking your doors the power will go to one wire or the other.

3) The pump in the trunk will either produce a vacuum (locking the doors) or pressure
(unlocking the doors)

4) Fuse 13 feeds the door lock circuit and there is a black/red wire from the fuse to the
door switch and then a blue wire and a yellow wire going from the switch to the pump.
The pump also has a brown ground wire.

5) The hose from the pump goes to a X fitting on the right side of the trunk and from
there one line to the trunk lock, one line to the fuel door lock and the other line goes
to another X fitting that is in a channel under the floor carpet in the front passenger
side. At this X fitting one line goes back and under the front seats to the drivers
side B pillar and then to the drivers side rear door lock, one line goes back to the
passenger side B pillar and then to that rear door lock and the last line goes forward to
the kick panel on the passenger side and into that front door and then the lock.

6) There is no vac/pressure line going to the driver’s door.

7) There is a vac/pressure pod in the drivers door (but see #6). This pod is there because
the electric switch is in the pod and that switch is moved by the door lock knob.

8) The door lock knob in the drivers door is the actural part that moves the electric
switch. The rod from the knob to the pod has the key lock attached to it via a linkage
(connecting rod and bracket from the key lock to the knob rod).

9) When the drivers door is open you can not press or pull the door lock knob, it won’t
move against the pressure/ vac.

10) The wires going into any of the doors are 20+ years old and can only bend back and
forth so many times before they break. When the wire breaks it some times only
separates inside the insulation so you can’t see it but you can usually feel it or find it
with a continuity tester.

I have never had to replace any of the tube/line or any of the fittings but I have had to splice in wire sections to almost all the wires for the locks, window and seat at the drivers door hinge area.
The picture of the pod from the drivers door shows the point where the knob rod connects, white part, and the point where the electric part plugs into it, black part to the left.

Last weekend the pump in my car stopped pumping although the motor still runs so if anyone has a pump they want to sell let me know.

mrmetalgear2000 · #14 08-30-2011, 12:00 AM

hi Phil.

Would it be possible if you could send me that schematic diagram of the central locking (300SD) you posted on this website to my email mr.metalgear2000@yahoo.com? I couldnt make clear the picture. Hope that when you send it to me it my be clearer when I download it.

thanks

Victro

yuke · #15 08-30-2011, 10:54 AM

I to have a problem with my locks on my 85 300SD in that I cannot lock the car with the key on the drivers side but on the passenger side I can.I did not know there is a motor in the trunk where is it located at?Where do you think my problem lies is it electrical or vacuum related?