Sorry you're in the forums with a problem.
Can you find a brand name on any of the heater system? Posting the system name would help.
Most DP use a small 12v pump to run the controls on the systems , so the first thing to do is check all fuses, that are powered up from the ignition.
Then , if all fuses are ok, you need to find the vaccum pump, about the size of a pop can, with hose and wire connections. Mine is on the out side of the firewall near the heater hoses. Then check for power and ground : ignition on; chances are it has failed , several suppliers for this pump , NAPA, Autozone , online or auto wreckers, Dodge P/Us with diesels used a similar pump from 2003.