The centrel locking system in my 84 190D is not working, I can here the vacuum pump working sometimes and sometimes it does not work at all. When it does work, it stays on for about 30 seconds. I know I have a leak somewhere, where is a good place to look? I checked the lines on the pump and they are fine. Also, why doesnt the pump work all the time? I have a different pump, I might try that.

it's best to isolate the various parts of the system, and track the leak down that way.
I use a vacuum pump, and connect the sections of tubing to it, looking for a leak...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

You may have 2 problems. A vacuum leak and a switch problem at the door. The 190D works on 1 vacuum line. The pump sucks vacuum ( negative pressure ) to lock and positive pressure to unlock.

You need a hand held vacuum pump, like a Mityvac to diagnose the leak. The vacuum lines are underneath the carpet. Try to look for T connections, remove the T and identify where is the pump side and where is the lock side. Hook up the Mityvac to the lock side and pump away. The door lock or locks should lock. If not then that line has a leak or the pod(s) downstream is faulty. Then work on other sections.

The switch is at the driver door. It could be the switch or the vacuum pump works intermittently. Change out the pump and if it still happens then it could be the door lock switch.

Good luck.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Thankyou, Where and what is the switch in the door? Also, there are vacuum pods in the locking system? I know there are vacuum pods in the dash, is that what you are talking about?

There are vac pods all over that car. There is one inside each door, possibly the trunk, the fuel filler door, ignition switch (for the shutoff).

__________________
1989 300E 144K

Vacuum has got to be the suckiest way for doing central locking... (ha! I made a funny) Seriously though, vac locking is as a 30 pound solution to a 20 dollar problem, these days.

I can't really complain because it is working in my car and I have 2 spare vac pumps so I'm set for life.... But if too much were to bust, I would seriously be looking at replacing with electric solenoids all around.

Has anybody looked at retro-fitting run-of-the-mill power locking solenoids and just tossing the vac control for central locking? If you had to go into each door anyway and check vac lines or pods ... and especially if a pod or two were found to be were duds. I would be pulling it all out and piling it onto the "saved weight" heap.

Oh... and I'd lube each window mechanism while inside each door.

__________________
Cheers!
Scott McPhee

1987 300D

Are you sure about that?

I am pretty sure but it all depends on which car. One does not need to be so sarcastic. You can add value to the forum by adding more info and not to withhold it.

Some old W126 does not have pod at the driver's door, just a switch. If the car can be locked from passenger door or trunk then it is pretty sure that there are pods at EVERY doors. The W123 has pod in every doors but the vacuum switch is only at the driver door, so you cannot unlock at the pass door. There are a number of variations with the vacuum central lock in MBZ so you need to know the car model. I find vacuum system reliable and reasonally easy to diagnose if you know how. The big drawback is a vacuum leak ( in line or pod ) affects the whole system while an actuator failure only affects a particular door.

My $0.02.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

The 190D has a vacuum pod at the driver door but there is NO vacuum line feed. The vacuum part is not used. The switch is an integral part of the pod. It is a 3 wires switch, one at 0V (chassis ), one at 12V and the other goes to the pump. When the pod is up, the 0V is siwtched to the pump wire and activates the pump to unlock. When the pod is down, the 12V is switched to the pump wire and activates the pump to lock. I cannot remember exactly the logic, the voltage could be the other way round to lock/unlock.

The pod is moved up and down by turning the key and making the switch. It is all mechanical. I spent a lot of time to put in a remote keyless control on my 190D. It is a PITA but it can be done. I need to install an actuator inside the driver door ( limited room ) to replicate the mechanical movement.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

What is the purpose of a vacuum actuator in the driver's door?

Let's do a little thinking here. If the driver door lock was vacuum operated, and the vacuum system failed, would that not cause a pretty big problem?

Unfortunately, "actuator failure" and "vacuum leak" are not mutually exclusive concepts.

What kind of thinking you are talking about, if there is one? LOL.

Please do not try to confuse the OP as he is talking about W201 chassis, a 190D which uses positive and negative pressure to unlock/lock. The W123 chassis uses vacuum reservoir and negative pressure only, if you do not understand, negative pressure is vacuum, to lock and unlock. It is a complete different design.

The W123 has a vacuum switch at the dr/door to switch the vacuum reservoir to the lock and unlock vacuum line. There are 2 lines to go to the pod. It may take one a lot of thinking to understand.

Please stop editing your post as you add nothing of value to this discussion. I am getting out as I have posted all I know.

BTW: When I meant actuator is the solenoid actuated actuator in modern car, voltage controlled, not vacuum controlled. Get it?

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

For sure, not the kind that causes you to just "think" that things are actually designed the way that you imagine them to be.

Maybe we should stop thinking and start betting. I have $1,000 that says the W123 driver door lock is not vacuum operated. And to add to the wager, if I am wrong, I will never post here again. If you are wrong, same applies.


Just one question. Who decided to toss unrelated models into the discussion?

I put a different vacuum pump under the back seat and the front locks work now but not the back, also found a leak at the trunk pod. Is there an easy fix, or do I have to get a new one? I am going to take it off and have a look. Any tips on how to remove and how to fix?

My problem was a hole in the diaphram on the trunk pod, when I plug that vacuum line the doors lock. Trying to seal the holes.

Hello 04 Diesel,

I have a '90 w124 & I believe our locking systems are very similar. Yesterday I removed the panel from the passenger door and removed the vacuum/pressure door actuator with the built in SPDT switch.

This unit does two things. First it either moves the plunger up or down depending whether the hose provides vacuum or pressure. Secondly the switch indicates whether the plunger is in the up or down position.

The SPDT switch is present (on my car) on the driver, passenger and trunk locks. If any of those locks are moved a signal is sent to the pump under the back seat (on my car) which sends the press/vac as required to open/close the locks. This also means it's quite easy to retro-fit a key-less entry for these cars by tying into the wires from the SPDT switch but that's another story (search here for more info).

Anyway my little black plastic unit with the diaphragm/plunger assembly and the switch was broken. I've ordered a replacement for $55. I'll be putting it in Monday. I'd say any where from 45 minutes to 2 hours to put it back together.

My w123 was different. IIRC only the driver's door will control the other locks and the system is exclusivelyy vacuum driven off of the reservoir. I don't have the car any more so I'm operating from memory.