Why won't my thermostat turn on?

Question

It's a honeywell digital thermostat, T8401C 1015. I bought another honeywell RTH230B programmable thermostat to replace it. After following the wiring diagram, The programmable thermostat did not work; then I put my orginal one back on and it did not work. I thought it might be a wiring problem, but I don't think so, the unit is 1.5 years old, gas heater and ac unit. the furnace switch is on, breaker is not tripped, I know the thermostat is not faulty. I connect the wires as follows:

G = Green wire
W = White wire
Y = yellow wire
R= Red wire
C = Blue wire

Am I wiring incorrectly or is there something else? Thanks

Answer 1

It's hard to say without being there. It sounds like to me you might have grounded a wire. If it's not working, you probally dont have control voltage comming to the stat. You might have blown the transformer for the control circuit. It's a new unit, so it might have a buss fuse or a control circuit reset. Hard to know without looking. Not a very bad problem, should not be much to fix.
Since you other stat does not work anymore either. That tells me its a voltage issue for sure.

Answer 2

To check the wires, jump the R and G terminal. Your indoor fan should come on. Jump R and W, the heater should initiate. Jump R and Y, the cooing should initiate. C is common power for the thermostat. NEVER CROSS R AND C. It will blow the transformer, or hopefully the fuse. Some use automotive-style fuses, some use the round style. Some transformers have a circuit breaker type reset on them.

If you don't get any response from jumping the wires, check the transformer or its fuse.

If the jumps do work, your T-Stat is questionable.