My 1979 240D (w123) has an issue with the driver door lock. When I manualy lock it with the door shut from the inside it locks but with the door open it will not lock. I guess if i need to lock it up I can just lock the driver side door from the inside and go out another door (look like an ass) but I would like to be able to lock my door when I get out of the car. I took the panel off the door yesterday and the vaccume peice with the three hoses coming out of it is all jacked up but it think the PO disabled that anyway.

I would just like to manually lock my door with the door open or shut, can anyone point me in the right direction.

Thanks in advance...

Will it lock with the key?

I'd look into sorting out the vacuum lock system. It's a really trick system when operating properly! Not sure about 123's but 116's lock/unlock all the doors plus the gas flap and trunk from the drivers door. It's creepily silent as well

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My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

With the door open the design prevents the door from being locked except with the key once shut. Normal 123 operation. When the drivers door is shut, you lock the door manually and all the other doors as well as trunk and gas door should lock by applied vacuum. You have nothing to fix unless once you shut the door and you press the lock button something does not lock.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

It does not lock with the door shut and trying to lock it with the key... (didn't try that). Don't really want to try to fix the vaccume system and would rater have a all manual car but I will buy a new vaccume piece if I have to ( the peice with the three vac lines) and troubleshoot any leaks.

Does anyone have a spare vaccume door lock actuator that works and hold vac that they would like to sell or know of a place that sells them cheap?

The door vac acutators are only about $20 on line. Do it right; fix the problem - you will be happy and that's the reason we all drive these cars.

The driver door simply sends vacuum to the other actuators. The 3 vacuum hose manifold does this. You have a mechanical problem with either the wrong key or the lock cyl within the door handle. Does this key lock the passenger door? does the key turn in the drivers door lock? And I agree, fix it correctly. Alot of these cars had their ignition lock cylinders replaced and some were not rekeyed so you had one key to start and one key to lock the car.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

The door is designed to only lock with the key from the outside or by pushing down the lock when the door is shut. If you want to lock it without using the key, shut the door, open the back driver's side door, reach forward and push down the driver's lock--it should lock all the other doors, then shut the back door. This process defeats the purpose of the system--which is to stop you from locking the door with the keys in the car.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The vacuum system is really pretty straightforward if you take a bit of time to figure it out. It can be frustrating to troubleshoot if you try to do everything at once.

Divide and conquer, and go in steps. Since the driver's door is giving you aggravation, start there. Get a Mity-Vac (or equivalent from HF) and start looking for the problem.

Then start thinking like a German. For example, the only reason you'd want to lock your door is because you just got out of the car. That means you were just driving, so the engine must have been running, which means there's a vacuum reservoir with vacuum. So...the lock switch actuates the vacuum mechanism the pulls the lock down. But you need a supply of vacuum to make that happen.

X2


X2


X2!

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I have this problem on my recently acquired 1980 300TD.

Only the master key doesn't do anything at all. It wont even turn, goes in, does nothing. So I guess I can't lock my doors??

The ignition switch wears over time. You've probably got a car where they swapped the ignition switch with an aftermarket or salvage switch and now have unmatched doors and locks.

Or your door switch was changed.

Check the "master" against the other locks. If they work, it's your door. If they don't, and you want a key cut then take your title to the dealer and he'll get one cut based on your VIN.

I think the keys cost about $10 from the dealer. If you want to go to a single matched-ignition and doors (and your doors are still OE) the dealer can cut a matching ignition switch, too. Costs about $100, though. Easy enough to swap out with the info available here.

Awesome! Thank you! It's definitely the ignition switch issue, the key doesn't work anywhere but the ignition. No biggie, I can have two keys for that price difference!