In a nutshell, from what I have learned from my 140.

The electric pump-based systems seem to have a single line running to each element from the pump. Sometimes there are multiple circuits, like one for the doors, and one for everything else.

There are also electrical switches in each lock lock or element. So for example, when you lock the driver's a circuit is closed (or opened) that tells the pump's control unit to apply suction to the lines to lock them. Same for unlock, except the pump runs the other way and produces pressure to move the elements to unlock.

So the drill is the same. Find the pump, find a place where you can hook up to individual elements, and exercise them with suction and pressure.

A little known fact is that a mityvac will produce pressure by through the vertical fitting generally covered by the little plastic cap. But unfortunately, the gauge only shows vacuum.

There are generally micro switches in each element that tells the control unit that the element has locked or unlocked. So if you lock the doors, and the control unit doesn't get a signal that the everything is in the lock position after, say, 10 seconds, it will shut the pump down. This is to prevent the pump from running continuously and frying itself.

__________________
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