Living in Mesa, AZ, and have central a/c with gas water heater and furnace. Removed older digital thermostat and installed the newer programmable RTH230B. Markings and wiring were the same and connected accordingly. Removed red jumper between Rh and Rc postions and left the J2 jumper setting in the HE position. After installation and breaker turned on, selected COOL and the little snowflake appeared but the a/c unit never came on. Rechecked all connections and nothing. Thinking I had made a mistake and against my own rational (RED for heat and BLUE for cool) reversed these wires and ran the RED to Rc and the Blue to Rh and the a/c came on and worked fine. Now with the cooler mornings, when HEAT is selected, the little flame appears but the unit never comes on, after even 5-10 minutes. I am in a delima now. I feel that if I reverse the wires (RED and BLUE) again the heat will work but then not the a/c. What type of system do I have? Do I have the J2 jumper setting wrong? Should it be in HG position since I do have gas heat but the heated air is distributed by the central a/c fan? Is the RTH230B compatible with my system noting that in the instruction manual it states "Note: These thermostats are not compatible with heat pumps or multi-stage systems".

When the gas tech came out to light the pilot, the heating system worked properly.

Markings are Rh, Rc, W, Y and G. (both thermostats)

Jonathan

If you can trace all wires from your tstat to the air handler to the A/C unit, I can give you a better idea what the blue wire is for. I suspect the red wire is your hot +24VAC. Don't know what the blue wire is for, so you could just try the red and replace the jumper on Rc Rh to see if that works.

Hooked RED wire to Rh and installed a jumper between Rh and RC and both work fine now. Don't know what the blue wire id for either? Beats me!