w123 vacuum locks

[Ya Mar]

Hello Everyone,

The locks on my w123 only go down when the car is running. If I try to turn the key in the door when the car is turned off, only the lock on the drivers side door goes down. All the others stay unlocked.

I noticed a w123 pull into a parking space next to me yesterday, the owner jumped out and turned the key to lock the door, and I could see all the locks going down!

Any ideas of why mine aren't working properly?

I wonder what needs to be repaired.

As I said, it works when the engine is running.

[Fattyman]

You've got a vacuum leak somewhere. You will need to track it down. Use the search function. (Vacuum leak, Vacuum troubleshooting, etc.)

[kerry]

Step one; Buy a Mity Vac.

[tangofox007]

Originally Posted by kerry

Step one; Buy a Mity Vac.

Or just move on to step two: replace your door actuators. If they are original, they are either leaking or soon will be.

[vstech]

nahh. if the doors work with the engine running, then the problem is in the trunk. pop the trunk, climb in, and look up under the window. notice that huge egg crate looking thing? follow the hose connected to it, and find the leaking connector.
that ought to fix it!

[Cr from Texas]

Originally Posted by vstech

nahh. if the doors work with the engine running, then the problem is in the trunk. pop the trunk, climb in, and look up under the window. notice that huge egg crate looking thing? follow the hose connected to it, and find the leaking connector.
that ought to fix it!

The leak could be several places. Mine was the fuel door lock and I had the same symptoms. Does the fuel door lock when the engine is running and you lock the doors? Also check the trunk lock. Lots of possibilities - get a mighty vac and start checking.

[ImBroke]

I agree with vstech. If they lock when the car is running, and not when it's stopped there is a problem with vac storage. I also agree with kerry in that it's mity vac time.

[tangofox007]

Originally Posted by vstech

nahh. if the doors work with the engine running, then the problem is in the trunk. pop the trunk, climb in, and look up under the window. notice that huge egg crate looking thing? follow the hose connected to it, and find the leaking connector.
that ought to fix it!

Apparently, you fail to understand that half of the locking system (either the "lock" or "unlock" circuit) is connected to the vacuum reservoir at all times. The significance of that fact is that a leak anywhere in the system will leak atmospheric pressure into the reservoir. Any notion that the problem has to be with the reservoir is erroneous.

Originally Posted by ImBroke

I agree with vstech. If they lock when the car is running, and not when it's stopped there is a problem with vac storage.

Of course there is a problem with vacuum storage. But that doesn't necessarily translate to a vacuum reservoir problem.

Originally Posted by ImBroke

I also agree with kerry in that it's mity vac time.

Door lock troubleshooting can be accomplished by simply isolating the actuators. No special tools required.

[Yak]

W123 Vacuum InterLock Diagram

Good pics and diagram in the above link.

I'd recommend starting under the hood and looking at the connections there. First, because it's easy to get to, and second because it's a common area for a line to get disconnected or cracked.

If you can't find an obvious culprit, then sequentially isolating the components is the next step. There may be more than one bad connection or actuator so it's not just a matter of saying "removed the trunk lock from the setup and it didn't fix it, therefore trunk lock is not the problem."

To isolate a component, you'll need to disconnect and cap both the lock and unlock lines. I've seen screws inserted into the rubber connections. It's an effective technique, but may damage the rubber if you use too large or too sharp a screw.

I'm a fan of the Mity-Vac with a pressure gauge because you can apply vacuum to a component (or series of components) and see if it bleeds down. HF sells a cheaper version of the Mity-Vac that is suitable, but less durable.