No Heat Part I: Quick troubleshoot of a faulty zone valve. When using a device like a zone valve, the “end switch” has to close to complete the electrical circuit, which is just one stop along the way of order of operations. In the case of a 24V control system like the old nasty one in the video, the end switch completes the 24V circuit to close a relay which then powers a pump and a gas valve. I’m not the best with electrical but I can usually diagnose equipment failure quickly because I unders