450SLC - Vacuum seat controls

[maldon]

The vacuum powered seat back locks do not work - nor does the central locking. From a quick inspection under the seats, all lines appear to be connected and sound.

Is this system generally prone to fail? Is there a quick test that can be done to ascertain where the system has gone wrong? If it is a major
job, has anyone any ideas how the vacuum controls could somehow be adapted for a simple mechanical method to engage/disengage the seat back locks.

Any advice appreciated.

 

[Rasputin]

Vacuum seat locks

Maldon,

Had the same problem in mine. I traced it back to the door vacuum switches which also controls the courtesy lights. These switches on the door pilars control the vacuum release valves to the seat locks hooks. Over time they make earth contact or loose vacuum via the connection at the switch. They come out by gently pulling them out and then clean any corrosion that may contribute to a bad contact. There seems to be a constant contact that tell the vacuum valves under the seats that the door is open. When the doors are open the hooks disengage to allow the seat back rest to fold forward. To test this problem turn the engine on, open the doors and press both switches fully in and the hooks should lock the seats (you will need an assistant to press the other door switch).
I solved this problem by glueying a type of rubber washer (without the hole in the middle) to the inner side of the doors where the switch niple is pressed by the door when closed, allowing the switches to push further in when doors closed. The seats hooks now works beautifully. It may also be the vacuum connection pipe rubber sleeve under the door sills (under the chrome strip on the door step).