R129 Central Locking System

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Rory129

New Member
Joined
Jun 17, 2019
Messages
10
Location
Renfrewshire
Car
300SL (R129)
Hi folks,

Mine is a 1990 300SL and I've been trying to troubleshoot the locking system issues I've been having.

So, what I've found so far is as follows:

Using IR key fob:

Drivers door - LED’s function, operates vacuum pump, does not lock/unlock any door
Passenger door - LED’s function, operates vacuum pump, does not lock/unlock any door
Boot - LED’s do not function, does not operate vacuum pump, does not lock/unlock any door


Manually using key in barrel:

Drivers door - LED’s do not function, does not operate vacuum pump, does not lock/unlock any door
Passenger door - LED’s function, operates vacuum pump, locks/unlocks passenger door only
Boot - LED’s do not function, operates vacuum pump, locks/unlocks boot only


Using internal door lock:

Drivers door - locks door, operates vacuum pump, can not use when door open.
Passenger door - locks door, operates vacuum pump, can use when door open


Manually using key in internal compartments barrel:

Operates vacuum pump, locally locks glove box and spectacles compartment (as can no longer press in either button), does not lock door compartments or centre compartment under arm rest.

It would seem clear from the above that I have a disconnected or loose vacuum pipe somewhere, any ideas where would be much appreciated thanks. I don't think it's behind the door cards as I recently had those off and made sure the two pipes were connected in each door before re-fitting.

I've had the vacuum pump/motor out and made sure all pipes were connected properly inside. The motor certainly works as I can hear it running for roughly 20 secs as per above troubleshooting.

My second problem seems to be the barrel in the drivers door not functioning at all with key (not engaging pump or locally locking door). I've tried taking this off for a look. But after loosening the small screw with an allen key the actual barrel is stuck inside the door and prevents me from pulling it out. Driving me nuts just now. :wallbash:

Not being able to use the key fob to remotely operate the boot sensor would be my third problem although the one of least concern right now.

Thanks in advance for any insight knowledgable folks might be able to provide. :)
 
Id be checking the vacuum at the locks firstly. I think (from memory) there is a vac cell at the lock that do leak. Your pump may also be inefficient too especially if its original.

You will need a new barrel for your door. Go to MB for that. It has probably beed bonded in when some bodywork has been done.
 
The locks on my R129 seem to take quite a long time to completely unlock the car. Both doors are fine but the rest of the locks, especially the boot, take around 10 seconds from when the key fob is pressed. Is this normal or should they all be super quick? I’ve never had any issues with it failing at all, just a little slow in my mind
 
You have a leak for sure, the pump is timing out, it should only run for 3 or 4 seconds with the system intact. Electrically disconnect the pump and go pipe by pipe doing a suck and blow test.
 

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