[merc81]

My scanner is not available at the moment, but you can't access the air pump motor directly. It gets power from an internal relay that can open to shut off the pump.
Motor power is supplied on orange wire to pin E with ground on black at pin G. The internal relay can fail open however so that's not a great way to test.


If its a 98, best to pull the whole assembly down from the van and put it up on the shop bench for a complete overhaul. The pump is a single piston type and it can seize up from moisture coming in with the inlet air. Nothing tricky on the pump assembly, you can pretty much just look it over and see where to start unscrewing. Open the crank shaft area and lube the under side of the piston and crank. Also, open the head area up and clean out the crap that builds up in there around the relay.
The head screws can be stuck, so use penetrating oil and maybe come back every day until they come free.
John