Just a while ago when coming in for the night, I realized I left something in the trunk and went back to get it. When turning the key to open the trunk, all the doors unlocked, then when I locked the trunk the doors locked too.

Problem is, this has never happened before; the trunk lock has never operated the doors since I have owned the car. I am very pleased but also a bit frustrated since I don't know what I did to cause this.

About a week ago my original key gave up the ghost and I got a new one, but I have only been able to open the passenger side door and the trunk, as well as turn the ignition. The driver's side lock is jammed, probably the result of my various attempts at lubricating and cleaning it when my old key started giving me trouble.

Also, I went on a crusade to remove the previous owner(s) leftover alarm and radio wiring (as you may have read in my other posts this past week) and had to re-connect wires to the vaccum pump.

So, I am wondering: Is using only the passenger door contributing to this, or did I correctly reattach vaccuum pump wiring that now enables the trunk lock to work properly?

Eric Silver
1989 260E

I suspect that you reconnected the wires properly, as mine always unlocks all the doors when I unlock the trunk.

The central locking vacuum pump (in a W124) is controlled by the front doors- and trunk locks. The vacuum pods in these doors and rear panel are partial vacuum and partial electric controlled. The electric wires from these pods go to the vacuum pump under the rear seat (at the right).

Alarm systems are normally connected to the wires of the front (preferable left) door(s).

My guess is that this (un)locking by the trunk lock is caused by the trunk's vacuum pod or connecting plug/wires.

As far as your problem with the left front door lock goes: order a new lock at the dealer (by chassis- or VIN#). You will get a lock that fits your original key and it will not cost that much.
You can take apart the lock as well to clean it, but that is only a temporary solution...

greetingz,

Just how much does a new lock cylinder and key cost? I have the same problem with my 420SEL. The driver's lock has not worked from the outside since I bought it, and the trunk has not worked the central locking system except for two freak occurances that I can not explain. The dealer told me a new lock cylinder would cost $1000. That is not cheap. Are they trying to rip me off, should it be less than this?

Thanks for the scoop on the trunk. It was actually kind of difficult to reconnect those vacuum pump wires since they are so short to begin with.

The only other thing that was a problem in the vaccuum system was the fuel filler door lock, which takes an unusually long time to open and close, and I can hear it hiss for a a while after locking or unlocking the doors. I have not listened to it since this trunk incident, however, but I assume it is still doing that.

I am certain that my driver-side lock is good -- just dirty from all the graphite probably jammed in there.

If I could get it out of the door I could blast it clean with a Water Pik (as I did for the passenger lock) but I can't remove it until I can get it to turn -- or is there another way?

Eric Silver
1989 260E

420SEL, 1000 dollars seems pretty steep, I think before I was a DIY I paid 300 or so. Fastlane has the whole lock assembly for $50.22. I could be wrong about yours they might have to drill it or something but that still does not come close to $1000 maybe an extra hour of so.

420SEL,
They try to rip you off; a door lock that is ordered by chassis# (fitting the original key) costs about $60-70 here in the Netherlands...).

Eric,
If you hear a hissing sound, the vacuum system is leaking. Check the trunk lid pod at the inside of the trunk (behind the trunk panel) to see what is leaking.
The locks consist of small parts (with even smaller springs) that fit the key exactly. If you lubricate or graphite these locks (a lot) it will only help you for a while till things get worse. If your new key fits the other locks but does not fit the driver's side door lock, you need to get it out and look whether it is worth to clean it again.
To remove the lock it is a lot easier when you can still turn it. You can remove a not turning lock after you have removed the door panel from the inside.

greetingz,