OK, I am going to fix my door locks! where to start? - PeachParts Mercedes-Benz Forum

vstech · #1 01-18-2007, 11:47 AM

On my 82 SD everything else vacuume related is working fine, shifting, shutting off, acc etc. door locks do nothing. I figure I will totally isolate the door locks and see if they work. suggestions are happily accepted.
John

justinperkins · #2 01-18-2007, 11:57 AM

I believe you want to start with the driver door, as that is where the master switch is located and a likely failing point.

This should serve as a good guide:
http://dieselgiant.com/mercedesmastervacuumswitchinstall.htm

jshadows · #3 01-18-2007, 12:00 PM

The FSM gives a pretty good description. But it works front to back.

1. Check valve in engine compartment
2. Driver's side vacuum lines to master switch and lines to doors (underneath carpet)
3. Passenger side front -> passenger side rear including rear door, tank lock, trunk lock
4. Driver's side rear door.

Have golf tees (about 5) on hand to isolate lines as you work your way back.

You need to check lock and unlock lines separately. It's all a process of elimination until to come across the leaker.

MityVac best, vacuum gauge doable.

Don't waste your time pulling the door apart unless you determine that the master switch is the culprit. My '79 SD poorly maintained still had the switch intact with no apparent damage.

Bill Ladd · #4 01-18-2007, 12:09 PM

Hey guys. He has an '82SD. Door lock vacuum comes from pump in trunk.

vstech · #5 01-18-2007, 12:21 PM

Quote:

Originally Posted by Lux

Hey guys. He has an '82SD. Door lock vacuum comes from pump in trunk.

I thought the pump was for backup... you mean it's the ONLY vacuum the doorlocks get? Hmm...

tangofox007 · #6 01-18-2007, 12:38 PM

Quote:

Originally Posted by vstech

I thought the pump was for backup...

No.

Hatterasguy · #7 01-18-2007, 12:42 PM

Quote:

Originally Posted by vstech

I thought the pump was for backup... you mean it's the ONLY vacuum the doorlocks get? Hmm...

Yep, make sure the pump works when you try to lock it.

vstech · #8 01-18-2007, 12:46 PM

ahh, when I first started driving this car last year, the pump used to run continuously when I shut off the car... now it does not. I better start there. the car used to have a bad water leak into the trunk. I have a spare pump, time to go.
John

Hatterasguy · #9 01-18-2007, 12:54 PM

You probably had a vacuum leak, this could have burned the pump out. The pump should only run when you lock the doors, it should not run at any other time on a W126.

tarbe · #10 01-18-2007, 12:55 PM

I am in this same boat.

I have confirmed that my pump works. I removed the vac line from the pump and put the mityvac to it and could not get any vac. Surprise, surprise.

Should I start at the door closest to the pump (PS rear)?

Bill Ladd · #11 01-18-2007, 01:01 PM

Quote:

Originally Posted by tarbe

I am in this same boat.

I have confirmed that my pump works. I removed the vac line from the pump and put the mityvac to it and could not get any vac. Surprise, surprise.

Should I start at the door closest to the pump (PS rear)?

Maybe start at the trunk lock and then gas door locks. Then hit the passenger rear door, etc...

its_snowing · #12 01-18-2007, 01:10 PM

yes, the pump in the trunk is the only source of vacuum. im working on my system right now, and am currently waiting for a new, used unit to arrive in the mail. there had been a leak in my trunk, and the wires ot the pump had correded, as well as some of the inner workings of the pump itself. very easy fix, and i got my used pump on ebay for $40. the proper model for my 82 sd was hard to find on there, though.

Bill Ladd · #13 01-18-2007, 01:12 PM

Quote:

Originally Posted by Hatterasguy

You probably had a vacuum leak, this could have burned the pump out. The pump should only run when you lock the doors, it should not run at any other time on a W126.

This is purely an elementary issue I'm suggesting here, so bear with me.

When I pirated my pump for the motor to be used in a keyless setup, It had a circuit board and what looked to me to be some sort of electro/vacuum relay. I assume the circuit board handled motor run times & direction and the relay was a shutoff to prevent motor burnout in case of vacuum leaks.

Of course, my board was burned out, so I was not able to test any of that.

My decidedly off-topic guess was that something went wrong in his control circuit which allowed the motor to run on due to the leak and that's what caused it to burn out.

I had a '95 Jetta for a while which had a leaking passenger door actuator. The pump would run for about ten seconds and the door would hiss before it shut itself off.

Not that that makes any difference in his situation or helps him in any way at all. Just trying to show how gosh-durned smart I am.

Hatterasguy · #14 01-18-2007, 01:33 PM

Its possible, I am not sure how the pump senses when to stop.

Johnhef · #15 01-18-2007, 02:14 PM

It stops when it sees a certain amount of vacuum. Unplug on of the lines and then activate it. It will run continously trying to suck it enough to lock.