I'm pretty good at wiring and testing circuitry. This is one of the ones that has gotten me obsessed. I've been installing Z Wave devices in my home, with very little problem and have been trying to install a Trane TZEMT400AB32MAA, so I can check and change my thermostat from my cellphone. I had been using a Honeywell battery powered thermostat, it could be model 9732. It worked fine and I've had to revert to it during this process. The Trane unit requires 24VAC, so I had to add a common from the air handler. I've installed everything according to instructions, and have 28VAC where it is supposed to be, between the C and the RH-RC, plus I have a W, a G and a Y going to the air handler. The problem is that I attach the unit to its backplate and I get nothing. No LCDs, no Light. I called the manufacturer and they said that if I put 24VAC to the C and the RC-RH pins I should see LDC reading. I tried it, with alligator clips and got nothing. So I returned the unit this week, and happily got the new one in the mail today. The result is the same. Do you have any ideas? If you're wondering, the Z Wave function does not come into play until I get the thing installed and working manually.
I saw somewhere on the web a note about checking the current on the 24VAC. This furnace actually has two air handlers ganged together and two transformers. I went to Radio Shack and bought a 28 volt light and socket to use as a load to check for current flow. When I tested it, I didn't see any, but as I write this I checked the continuity of the light and see that it is open. I don't think I had enough resistance, and the thing was burnt out before I got back to the thermostat. The mystery continues.
Last edited by TommyTelephone; 09-13-2009 at 12:05 AM.
Reason: An additional note