Been trying to get my central door locks working. Seems like I have good vacuum with no leaks. I say that because, when I first plug the pump in it will run about 10 to 15 seconds, locks will all lock and pump will shut down. After fooling around with my old pump I could get the doors to work for about a week then nothing, pump would not come on at all.

Thinking I had a bad pump I ordered a used one. Plugged it in, pump runs for about 10 seconds, shuts off, and will not activate again by turning door lock.

Could it be that I have two bad pumps. or is my problem something else? Seems like the problem is in the vacuum/pressure switch not resetting. Can anyone tell me how this circuit works?

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1989 300E
103,500 miles

1982 300SD
Sold but not forgotten

I'm thinking you have a vacuum leak somewhere that is causing the sequence pressure switch to bleed off. The best way, might be to "T" a mighty-vac into the system right at the pump, lock the doors and see if the vacuum stays constant. (The sequence pressure switch, on the supply pump assembly, switches the polarity for the supply pump.)

Mine had problems until I replaced a flex line at the pump. That might be the first thing to try.

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Sam

84 300SD 350K+ miles ( Blue Belle )