Tech Support Forum - View Single Post - Thermostat wiring

icer22x · 02-22-2009, 12:38 AM

Howdy guys,

Hopefully someone here knows about thermostats.
I moved into an apartment that has your typical everyday three-layered Mercury switch thermostat.

(Fan control set to auto)

I've done a little research on the wiring for this type thermostat, but some seem to vary.
Anyway, I was wondering how to completely disconnect the heat so when I switch the thermostat to heat, nothing happens. I know I can just turn it off, but I am running some diagnostics.

I have two red wires running out of the wall and connecting to the RH terminal on the circuit card. From the research I have done, this seems to be the power to the heat control. But nothing mentions TWO wires like I have. Anyways, I have disconnected these two wires from the RH terminal and reassembled the thermostat. I switch it to Cool and I can hear the AC come on. All good. But then I switch it to Heat and I can hear the darn thing fire up.

Is there something I am missing? Is what I am hearing just the fans coming on and the furnace is not getting power to heat up (like what I want to happen)?

Thanks in advance for any help!

02-22-2009, 12:38 AM	#1 (permalink)
icer22x Registered User Join Date: Feb 2009 Posts: 34 OS: Windows 7 32-bit	Thermostat wiring - need help Howdy guys, Hopefully someone here knows about thermostats. I moved into an apartment that has your typical everyday three-layered Mercury switch thermostat. (Fan control set to auto) I've done a little research on the wiring for this type thermostat, but some seem to vary. Anyway, I was wondering how to completely disconnect the heat so when I switch the thermostat to heat, nothing happens. I know I can just turn it off, but I am running some diagnostics. I have two red wires running out of the wall and connecting to the RH terminal on the circuit card. From the research I have done, this seems to be the power to the heat control. But nothing mentions TWO wires like I have. Anyways, I have disconnected these two wires from the RH terminal and reassembled the thermostat. I switch it to Cool and I can hear the AC come on. All good. But then I switch it to Heat and I can hear the darn thing fire up. Is there something I am missing? Is what I am hearing just the fans coming on and the furnace is not getting power to heat up (like what I want to happen)? Thanks in advance for any help! Last edited by icer22x; 02-22-2009 at 12:42 AM.