I have a 1995 W140 S420 with a bad central locking pump (PSE pump), or at least I think I do.
Symptoms...
1) Everything using vacuum off that pump is dead...door lock, trunk latch, fuel filler door, etc. 2) HVAC vents seem to go into "fail safe" mode upon acceleration - I've read where this pump provides extra vacuum for the HVAC system when needed. 3) With rear seat and protective foam box removed, I can hear what sounds like a relay actuating in the pump...a "solid" click, whenever I think the pump should be turning on and off. I do not hear or feel the motor run, like I can with the closing assist pump under the same circumstances. 4) Just to be thorough, I checked and get no vacuum on any line from the pump at any time. 5) Yes...I checked the fuses.Questions...
1) How can I do a bit more incisive debugging ? I can't make sense of what alldata.com has. I would at least like to check supply voltage and a control signal or something. Anybody know the pinout on the pump? 2) Assuming I have to buy a new one, I checked and found it offered on at least 8 different websites. I found a high of $569.20, 5 at $485.6, 2 others in the $400's, and one at $292.00! My unit matches both the Bosch and MB parts numbers of all the websites. I'd obviously like the one at $292.00 but I'm wondering what I'm missing if everyone else wants 200 bucks more. The site isNotes... I took the pump out in order to try to play with it and maybe rebuild it (a la the duovalve rebuild of Pete at