I know there is other posts on this subject and I have read them. I am having a problem with the locking system on a 260e 1987. No voltage at pump...tried taking pump out and apply voltage from another source....pump does not run. Is it suppose to with volts applied? The vacuum lines are tight, I can actually lock and unlock with manual slight pressure or vacuum. Fuse is good. I can find the no volts problem with some effort. Why would the pump not run with external 12VDC applied? Two problems here? Locks were giving me a problem when it got real cold but worked after car heated up. Now....nothing. Any input on this would be greatly appreciated. Thanks!

Either the pump is broken or the fuse is blown.

Applying 12V to the pump will not make it run by itself. Another 12V or ground is needed on one of the other pins

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

The pump is bi-directional. It provides positive pressure in one direction, negative (vacuum) in the other. It needs not only 12V to run, but also information as to which direction. The sense leads are touched momentarily (1-2 sec) to either 12V or ground to choose the direction. An internal flow/pressure switch turns it back off.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Tried the locks the very next day and they fired up. I'm going to check the b+ connections that supply power. Guess the pump is okay. Someone posted here about the subject and it was very helpful. Thank you all for the replies.

Read my posting, it should be informative (it has some pictures)

__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified