R129 central locking sucks, or does it blow?

[Jubag]

Good evening, I am in the process of fettling my newly acquired 1990 300 SL, at the moment I have removed and stripped the central locking pump from the boot. Half of the entire aluminium head of the 540 type motor has melted to nothing, so I have no way of knowing what polarity the yellow or green wire are.

My question is this... can anyone tell me which action ( lock/unlock) creates vacuum/plenum?

If I can establish this I can get the wires on right first time.

[ras62]

The whole system operates by vacuum only. Lots of tutorials on youtube etc

https://www.ifixit.com/Guide/Mercedes+W123+Vacuum+...

[Jubag]

Ok, that's interesting, when I put a motor on the wires and turn the key to lock or unlock the motor goes one way, then the other. I will read that article as I'm now confused!

Thank you.

Edited by Jubag on Saturday 14th January 23:06

[Jubag]

Ok, that's interesting, when I put a motor on the wires and turn the key to lock or unlock the motor goes one way, then the other. I will read that article as I'm now confused!

Thank you.

Edited by Jubag on Sunday 15th January 14:07

[ras62]

Sorry Im giving duff info! The pump does produce vacuum and pressure, The youtube videos are quite good explaining things

[Jubag]

I have just put a multi meter on the wires and when I lock the boot the yellow wire is positive, and the green wire is negative.

When I unlock the boot the green wire is positive and the yellow wire is negative.

Can anyone tell me which way it's sucking or blowing for lock/unlock?

It's amazing how much of the car is vacuum operated, I've even lost my dash vent operation!

[PositronicRay]

The A/C fault gives a clue.

The ventilation system is powered by the engine vacuum. I believe the two systems are interlinked though, with a vacuum reservoir. A leak could have caused the vacuum pump to burn out as well as ventilation A/C problems.

If you look @ the vacuum diagram you'll find a distribution block, known to split and cause problems. I think it's located on the passenger side near the main engine ECU.

Try posting here, some very experienced and knowledgeable people posting on this site.

http://www.benzworld.org/forums/r129-sl-class/

[Jubag]

Will do, thank you all.