Doors Lock automatically 10 seconds, 85 300SD - PeachParts Mercedes-Benz Forum

biopete · #1 03-14-2006, 11:18 PM

I just got an old beater 85 300SD . I must say, I am completely enamored with the Turbodiesel engine and the roominess and the reading lights in the back. The W123 felt nice and compact going to work yesterday morning after spending all weekend in the W126. Still love the look of the W123 and the simplicity.

I am not enamored at all with the big spaghetti mess of electronics and vacuum lines under the hood. Especially how my doors lock automatically 10 seconds after i unlock them. I read the owners manual and did not see anything about this being a feature. Its annoying as I have to keep a door key outside at all times and have to keep unlocking it at the trunk every time i need to get in. Can anyone shed any light on this? Oh yeah, i wonder if this is connected to why the front passenger door loock never locks but the knob is disconnected so it looks like it is locked? The po said "It sometimes does not lock with the rest of the doors" and i have yet to see it lock at all.

Oh yeah, 2 nights in a row now it does stay open. But all day, i cant figure out how i make it do that. Is there something that locks doors automatically, like a keyless entry sensor being triggered all day and at night it is not?

More sordid details -- I dont have a master ignition and door key, just an ignition key and 2 master door keys but they only fit the trunk and the glove box and not the front doors it seems. I have to lock and unlock everything at the trunk.

thanks

oor

pawoSD · #2 03-14-2006, 11:39 PM

The circuit board on the pump in the trunk that runs the locks is probably malfunctioning and running the re-lock cycle on its own. Check all the connections for corrosion/good connection etc. Its in that rubber football in the spare tire well of the trunk.

For the keys: The "Master" Keys have a square head, and will open and work in every lock on the car, the "valet" key will work in the doors and ignition, but not the glove box or trunk. The valet key has a circular head.

Lycoming-8 · #3 03-14-2006, 11:54 PM

It sounds like one or more of the tumbler sets has been changed, and that is why the keys do not seem to fit the doors etc as they should. As previously noted master key should do all locks incl 'ignition', while valet key will only do people doors and 'ignition'. The auto lockdown may also indicate that some of the vacuum lines have been hooked up incorrectly. Does unlocking the drivers door not unlock all of the doors etc at least for a moment?

SD Blue · #4 03-14-2006, 11:58 PM

That "spaghetti" of vacuum lines under the hood has no effect whatsoever on the door lock system of the w126. The separate vacuum/pressure system in the trunk drives it. The driver's door lock is the "switch" that controls it. Try here: http://mb.braingears.com/ for diagrams.

biopete · #5 03-15-2006, 12:03 AM

Quote:

Originally Posted by pawoSD

The circuit board on the pump in the trunk that runs the locks is probably malfunctioning and running the re-lock cycle on its own. Check all the connections for corrosion/good connection etc. Its in that rubber football in the spare tire well of the trunk.

For the keys: The "Master" Keys have a square head, and will open and work in every lock on the car, the "valet" key will work in the doors and ignition, but not the glove box or trunk. The valet key has a circular head.

great info thanks. Regarding keys, i thought i read there are 3 different types of keys -- a master key with red dot that does EVERYTHING, a valet key that does doors and ignition, and a master lock key that does all locks but know ignition. I will test thouroughly and figure out what i have. I now can only lock and unlock from the trunk. The lock keys are thicker than the ignition key.

thanks

biopete · #6 03-15-2006, 12:18 AM

Quote:

Originally Posted by Lycoming-8

I Does unlocking the drivers door not unlock all of the doors etc at least for a moment?

It does when I am on inside. I cant use that from outside as key no fit.

Lycoming-8 · #7 03-15-2006, 02:09 AM

If none of the keys actually fit in the drivers door, that pretty much settles it that the ign key was likely changed. A lot like my situation, where the ign tumbler and key was changed. Now we need to use two keys to operate the car. The old (orig) ign lock and all was in a box in the trunk, but will not likely prove to be useful for anything.

MBeige · #8 03-15-2006, 02:36 AM

I would imagine that a vacuum line has been routed into a loop? Or something has been linked in conflicting directions which gives you the 10 second delay until it engages again. Check vacuum fittings (Y and + shaped)

Do you have a yellow vacuum valve on/near the firewall? It's a 1:3 connection, I believe. Originates from the brake booster line and into the yellow valve, and then into the firewall via a brown, red or green (with yellow) line. Not sure if it's exactly the same but I would imagine it's similar.

pawoSD · #9 03-15-2006, 02:43 AM

Quote:

Originally Posted by MBeige

I would imagine that a vacuum line has been routed into a loop? Or something has been linked in conflicting directions which gives you the 10 second delay until it engages again. Check vacuum fittings (Y and + shaped)

Do you have a yellow vacuum valve on/near the firewall? It's a 1:3 connection, I believe. Originates from the brake booster line and into the yellow valve, and then into the firewall via a brown, red or green (with yellow) line. Not sure if it's exactly the same but I would imagine it's similar.

The engine vacuum system is completely separate from the locking system in a W126. They have a separate electric pump in the trunk that handles the locking/unlocking. It is triggered by a switch in the drivers door lock assembly, or by both the driver door and trunk locks on 1984 and onward models.

MBeige · #10 03-15-2006, 02:46 AM

Forgot about that one.

Thanks for reminding me

biopete · #11 03-27-2006, 02:55 PM

Not sure what the problem was yet. My "friend" who was in need of a good working pump had the idea we take out pump and see if it works in his car.

Well, he is using it now and it works great. And my doors dont lock automatically. And my friend owes me a good favor or part now (I'm thinking trailer hitch welding ) as those things are expensive and mine looked perfect.

Door locs are the least of my concerns with this beater for the next few months.