Thanks Diseasel300. Yes, the vacuum pump is controlled by fuse #13. I've measured this fuse and there is voltage on both sides of the fuse with the ignition off. So I have 12 VDC at the fuse as well as the 2 pin power connector at the pump.


There are three other wires which connect to the second pump connector. They are yellow, brown and green. I assume these pass voltage to the pump from the switch in the door. It appears that these wires control an internal switch within the assembly so the pump is doing vacuum or pressure.



A trouble-shooting method might be to run a ground and hot wire to the pump from a seperate battery. MB's have issues with grounds in my area due to moisture. Then run a seperate jumper to one of the three posts on the second connector. I should here a switch snap and then the pump run. Is this thinking correct ?