Heater control valve solenoid

Hi, my rear heater was not working properly so I felt the hoses to the heater core and one was hot, the other warm. I realized that the heater control valve was not getting vacuum at all. I followed the vacuum line up to the heater control solenoid and obviously it is not working. The vacuum line on the top of the solenoid is drawing vacuum. The htv vacuum line is not. I checked the two wire electrical connection to this solenoid and checked it with a test light and it shows nothing. One of the wires to this solenoid should be hot, right? I don't want to replace the solenoid if it is not faulty. I am not sure exactly what do do at this point. I believe the hcv is not faulty, as it is a simple device which works off vacuum. My concern is the device on the firewall that the vacuum lines connect to--the electrical connection to it. Thank you. Dave.