diagnosing door locks - PeachParts Mercedes-Benz Forum

dunl · #1 02-26-2006, 09:09 PM

1980 300SD

Bought this with non-functioning door locks. After working on the shut-off vavle leak, I have decided to jump on this one. First some info:

1) Door locks do nothing at all, except for the pull handle/knob locking thingies (feel free to name these for me) are in the upright position, and remain so all the time. The drivers one is completely disconnected, and can be lifted out of the hole.

2) Pushing down to lock the doors is prevented by heavy resistance. I say resistance, as it SEEMS to move a slight bit downward, but I'm afraid to go harder and break something.

3) Yellow line and yellow line with brown stripe going into the cabin through the firewall. Yellow line appears to have excellent seal - its counterpart with the brown stripe appears to have heavy leakage. I haven't been able to source a MityVac locally in my area, so I simply sucked on the line. While I can feel suction on other lines I have tried, and tell if there are good seals, this line feels like it is completely disconnected somewhere, and I am simply pulling as much air through the line as can be pulled - without resistance of any kind.

4) Key does nothing to the locks. Works to manually open and close the trunk.

I'm wondering if the levers for the locks on the doors remaining in the upright position are a symptom of anything particular, rather than just a symptopm of something being wrong.

Also, what is the best way to track down this problem? I can simply start ripping apart the doors on the vehicle, but if there is a more intelligent way to go about it, that would help a lot.

Thanks,
Dunl

mbzkid · #2 02-26-2006, 09:36 PM

Where do the yellow and brown lines go? I'm having the same problem.

I think the next step would be to check each door for a leak by applying a vacuum to the lines that go to each door. If its like a 123, you should be able to tap into the lines under the drivers side carpeting against the rocker.

I don't have a vac. pumps so thats as far as I've gone.

dunl · #3 02-26-2006, 09:45 PM

The lines go through the firewall and on to the doors. The one with the brown stripe leaks like a sieve, and appears to go directly to the driver's door....so I am guessing that is the best way to start. Mine go through by the door hinge, so under the carpet is out of the question.

I believe I also do NOT have the vacuum pump in the trunk, like the later models do.

trueog · #4 02-26-2006, 10:32 PM

Quote:

Originally Posted by dunl

The lines go through the firewall and on to the doors. The one with the brown stripe leaks like a sieve, and appears to go directly to the driver's door....so I am guessing that is the best way to start. Mine go through by the door hinge, so under the carpet is out of the question.

I believe I also do NOT have the vacuum pump in the trunk, like the later models do.

My Vaccum pump also gave out. It's in the trunk. However my anti-theft lock kicks in... Since the power locks are now dead, I have to manually lock and unlock, the key works fine. However if I get out of my car, quickly unlock my trunk, change the cd's in the disc changer, lock the trunk, jump back in, the car won't start. The Anti Theft will kick in! and my car simply doesn't fire up and responds as if its dead. To get around it, I have to jump out, and unlock the driver side door with the KEY!!!(important) and this will over-ride the lock down and the car will start perfectly fine. I don't know if your car has anti-theft on it, but I thought i'd share incase someone else ever comes across the same problem and wonder why their car just died...

Mercedes Richmond quoted me $1300 for the Vacuum pump. They warned me that until they check out the wiring and do a pressure test on the car and correct the leaks that may have that caused the pump to over work and fry itself, it's pointless to replace it as the new one will burn out within 6 months also. $1300 CDN, plus 5 minutes labour to change it...and god knows how long to detect wire leak and correction(they wouldn't even take the chance to taking a guess).....scary...

mbzkid · #5 02-26-2006, 10:36 PM

When I said vac. pump, I meant a hand pump, to test the lines.

Lycoming-8 · #6 02-26-2006, 10:53 PM

Dunl,

"4) Key does nothing to the locks. Works to manually open and close the trunk."

Can you even move the key to the left or right in the door lock slots? If not it is possible that either the "ignition" lock or the door locks have been changed. Original keys worked on all locks if they were the master and on the "ign" and side doors if they were the "valet" key. What about the glove box, does your key open it?

dunl · #7 02-26-2006, 11:32 PM

The key actually works fine. However, it doesn't produce any result, whatsoever. I took the door panel off the driver's door, and it appears that the little notched point on the end of the lock mechanism does not come into contact with the door opening mechanism whatsoever. Looks like that might be a culprit.

Anyone have a diagram of the door locking mechanism, and how it is assembled?

Thanks,
Dunl

dunl · #8 02-27-2006, 08:17 PM

Quote:

Anyone have a diagram of the door locking mechanism, and how it is assembled?

I'd also settle for someone telling me if the notched end of the part that the key turns is supposed to have something IN the notch.

Thanks,
Dunl

PS. If someone could possibly troubleshoot why the locks are frozen into place as well, that would be helpfull. Thanks.

dunl · #9 02-27-2006, 10:09 PM

Help me.....help me......heeeeeellllllllppppp meeeeeee
(from the movie "The Fly" - lol)

dunl · #10 03-01-2006, 01:07 PM

Bippity-bumpity-boo. Still looking.

Diesel Giant · #11 03-01-2006, 06:40 PM

Are you sure the linkage inside the door is not binding?

dunl · #12 03-01-2006, 09:28 PM

Okay, partial problem seems to have been lubrication, as I cracked open both door panels on the front and lubricated the locking mechanism.

However, the driver's side lock doesn't even seem to be attached to the opening mechanism - that's why I am looking for a diagram.