W124 Lock System Question
 

The locks all work manually, but not automatically.

Sorry for the vague question, but I know nothing of this system on the W124's. Where do I start?

When the lock system on my 300D (W123) went out, it was as simple as reattaching a vacuum line in the engine compartment. But I have been told that these are not the same. :confused: :confused:

There is a central locking pump under the rear seat.
Creates vacuum to lock the car & pressure to unlock.
There is a single yellow line that goes to each door & to the gas flap & trunk lock.

Diagnosis starts at the pump.

Great. Thanks!

Access from under the car?

Since you have a T124, not a W124, it is under a carpet piece beneath the right rear seat and you will probably have to pull the threshold plate to access it.

Do you hear the pump cycle when you lock and unlock the front doors? It should be a faint compressor noise, hard to hear unless all else is quiet (tip the right rear seat forward to listen).

If not, it could be either the pump, a fuse, or a switch. There is a switch in the actuator in each front door, and one in the hatch, any one of them should run the pump (try all three if you can't hear the pump).

If the pump is running, the next step is to apply vacuum / pressure to the system to see if it is an air leak, which could be any of the (6) actuators or a line/fitting. Open the rear cargo compartment where the jack is stored, you'll find a yellow line leading to a rubber tee. Hook up a vacuum/pressure source at this tee and apply vacuum & pressure, locks should actuate. If there is a leak, you will be able to narrow it down by the three lines which go to: hatch, fuel-door, all doors including vacuum pump.

Common leak areas? None really, but I'd suspect an actuator first, then possibly a line damaged in a door-jamb, last would be the lines in the floor.

Good luck, I'm going through this again also.

AWESOME. Thank you. I will get on this soon. :)

Welks.

Although I haven't experienced it (yet), it seems that the line across the hinge to the hatch is particularly vulnerable.

Sorry to piggy-back a question, your answer reminded me...but does this same pump control the "silent rear gate" option? When I was test driving some of these, all of them had this feature that when you shut the rear gate, it was sucked in so that it wouldn't slam to shut.

Mine doesn't do that. It just shuts.

Nope, electric pull-down motor.

OK. Thanks. Do some not come with that? Or is mine broke? It seems to shut pretty normal.

I really appreciate your help.

They break, and all US 124 wagons have it.

Common leak areas (as the car ages) are usually the rubber connectors at every vacuum intersection. I have come across many w123s and w126s (including both of mine) with this issue but not too many w124s so I wonder if they improved on it the material at all for the later chassis.

Ok...seems that I have a better description of what is happening:

When using the key from the outside, only the door with the key is locked and unlocked.

When unlocking/locking the car from the inside with the car off, only the door with the key is locked and unlocked.

When unlocking/locking the car from the inside with the car running, ALL doors lock and unlock (system works).

When opening the door and the car is off, but the doors are locked, ALL doors unlock when you open the door (system seems to work).

Ring any bells?

Would really love for this system to work!!!

Still nothing? Still having this problem.

18 months later you are still having the same issue? :confused: Have you located the pump under the driver's side rear seat? You access it from inside the car not under neath. As Babymog said, flip the seat up to access it. It is under the carpet so you will need to pull that up.

Yes I am.

I don't mind going to the pump, but it works at certain times. It's fairly predictable as I mentioned above.