190e no heat
 

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?

Does sound like a vacuum issue, but no pump.

Uses engine vacuum & a vacuum manifold to distribute vacuum to vacuum diaphragms that move flaps on the heater box.

no heat
 

I believe you are saying that the little box on the fire wall should have a hose connected to it for a source of vac. It is possible with the motor swap, I/we missed a hose? The motors were a little different. There are no hoses available to connect to this unit. It does not have a hose barb for a connection. The electrical connector is a two wire that traces back to the vac cannister in the heater hose line. It sure looks like a little pump.

The only electric pump like you describe is the auxiliary water pump, pulls water thru the heater core.

The vacuum hose that goes through the firewall is for the vacuum control unit for the pods. Follow it through and ensure it is connected to the intake manifold somewhere. It uses engine vacuum to control the pods opening/closing.
Another easy way to check is to grab a flashlight and look down the main center vent. Start the car up and watch to see if it opens after 1minute or so. If not, more than likely the vac hose is disconnected somewhere.