I took the new diaphragm from the MTC unit and installed it on the OEM (Bosch) unit and now I have heat on demand. I also have cool air on demand as well as moderately warm/cool air on demand. I’ve unplugged my auxiliary water pump because it is no good. I removed it and connected 12v to it and couldn’t get the motor to budge. I also disassembled it for cleaning. The motor moves freely, but it doesn’t work when given 12v. It’s reinstalled just to keep the stock plumbing for now. I will replace it...eventually. It’s definitely not a pressing matter.