Thanks for the long explanation. That was very helpful in filling in the gaps.

I plugged both P- (vacuum only) and P+ (pressure only) and still have the cycling problem, which indicates to me that there is a problem with the control unit's internals. Maybe there is an adjustment in the little round "paddles" that close the contacts that will help. My next step, as syljua suggested is to watch it run with the cover off.

But what I also did was to disconnect the lead to Pin 4 on the wiring harness. This is the power from Fuse 11 in the trunk (hot with key on), which seems to enable the P- and P+ trimming. Now I have locking, trunk open, and reverse assist and the pump seems to function normally (runs briefly when each function is exercised). So this resolves the major headache of not being able to lock the car from the driver's door and will allow the car to be driven while I sort out the trimming problem.

What I suspect is a ruptured diaphragm as was discussed in the close assist article on Pete's website:

http://v12uberalles.com/Closing_Assist_Pump.htm?

I will replace the element in the driver's door ASAP, but it still locks/unlocks OK with the key and the pump does not seem to mind.

Stay tuned.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe