I have a 93 190E 2.3 motor. I had a heater hose blow on the highway at a very high rate of speed. Lost the head gasket. The best solution was a new motor, considering the miles on the original motor(300k). It runs very well. Everything works except for cabin heat. The defrosters work great. It talkes a minute for the hot water to get the core hot, but then produces heat well. When switched to regular heat, I get nothing. The control vacuum for this system comes from a unit on the fire wall. This device has an electrical connection, and two vac lines comming out of it. One to the tranny and the other to the controls for the cabin heat. This little black box is mounted on the fire wall, drivers side, very near where the heater hose split. My guess is that little unit is a vac pump that is not working properly due to the split hose, and the reson I have no heat. All worked perfectly before the hose split.

Am I right that it is a vac pump and the source for the control vac for the cabin heat? For ordering purposes, what is this unit called?