i recently purchased a 72 280SE that is in need of alot of tlc. i have since got it running and stopping better than it was, and am now going over the car, fixing all the small problems and i come across them. my question is about the central vacuum locking system. my problem is, the two keys i got with the car dont operate the door locks or the trunk lock. i can push down all the door lock pins minus the drivers door from inside the car, but i cant get the key to do anything in the drivers door or the the passenger door. for the time being, id like to just use the key to lock the drivers door from the outside as i can just push down the pins from the inside when i need to lock the car when its out in public. now the thing i dont know is, the car at sometime in its life couldve gotten a new ignition switch, which i imagine would come with its new own key. does this sound like something that wouldve happened? i took the door panel off the drivers side door and removed the 3 vacuum lines to see if i could bypass the central locking system that way, but it did nothing. im starting to think i dont have the proper key for the door locks. am i doing something wrong or over looking something major here? any help would be greatly appreciated.

well i fiddled with the locks some more and found that the key i do have DOES fit and will lock the door. i ended up spraying some pb blaster in each of the tumblers as well as white lithium grease on the moving parts behind the door card and i can now lock and unlock the drivers door, from the outside, with the key. the other 3 doors i can lock by pushing down the pin inside, so i can now park my car in public without giving *******s ease of just opening the door. i do plan on eventually fixing the vacuum locks, however, this will get me by in the mean time.

the tumblers do get gummed up , I would suggest now that you use compressed air and blow them out and lube with grahpite powder or you will end up the in same boat, and in the winter you will have a mess . The main cause for tumbler issues is that dirt and grime and the key itself ( wearing) cause them to stick or not turn properly. If you get a new key cut or you may find it will work better
Also the first place to look at vacuum locks not working is the 3 way valve in the drivers door. 8/10 that is the culprit, followed by broken, loose lines

__________________
Ron
2015 Porsche Cayman - Elizabeth
2011 Porsche Cayman - Bond,James Bond
Sadly MERCEDESLESS - ALways LOOKING !
99 E320 THE Queen Mary - SOLD
62 220b - Dolly - Finally my Finny! Sadly SOLD
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
19 BMW X5 - Heaven on Wheels
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace

On my 108, the issues with the door locks were the rubber diaphragms on the locks themselves. All 6 had major tears so they wouldn't lock or unlock. You can get replacement ones, or you can probably seal your existing ones with silicone like I did. A thin coat over the whole thing held for years.

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

I know these are old posts but looking for some help in how best to get the door cards off to repair the locking system since none lock. Appreciate any feedback so I can lock it in public. John

This is a good how to video, he does it on a 109, but it is essentially the same door card. Actual removal process starts around TM 3m:10s.

https://www.youtube.com/watch?v=vJhJ7HjTG8g&t=1476s

a good set of body work pry tools is a must if you want to not damage any of the fasteners. Unfortunately some will break no matter what. They can be had , but will take some searching

__________________
Ron
2015 Porsche Cayman - Elizabeth
2011 Porsche Cayman - Bond,James Bond
Sadly MERCEDESLESS - ALways LOOKING !
99 E320 THE Queen Mary - SOLD
62 220b - Dolly - Finally my Finny! Sadly SOLD
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
19 BMW X5 - Heaven on Wheels
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace

When I have run into this door locking thing I just remove the door latch assembly and clean it. The tricky part is a small spring near the bottom and the only thing to remember is not to put any pressure on it or it will break.

Just clean everything, spray it with some lube, and they will start to work like new again.

For those who have forgotten (or never knew), locking the driver's door only with the key and not by depressing the interior knob and shutting the door is a safety feature designed to keep the driver from locking the keys inside the car.

I ran into this on my first Mercedes. At first I thought something was wrong but then I realized just how well thought out the car was.