I installed this termostat replacing an older programmable 5 wire model that controls one of my central air/heat units. I installed the same model last year. I checked the wiring on my other unit, wired this one the same, programmed it and turned the heat up until it displayed "heat on" on the thermostat without any response from the furnace.

I've checked the power switch to my air handler/furnace and it is on, then checked the breakers without finding any issues. Since the red wire is the 24 volt source, does it matter if it is in the RC or R slot as long as they are bridged with the metal jumper wire? I have heard you can jumper across two wires to cause the unit to come on but know know the specifics. I don't get an error codes on the thermostat but think I may have a power issue. I have heard others mention fuses but don't know how to access and I have not checked out the stepdown transformer or air handler at this point.

Any help is appreciated.

Does the furnace do anything? Does it have a automotive type fuse in the curcut board that's OK? Are you 100% certain the new tstat is wired correctly? It may be time to check for a fried transformer,, this is just a few things to get you started
Also it wouldn`t hurt to get the name,model numbers of your equipment and post them

Thank you wmproop.

I have a goodman system, made here in Texas. I checked the fuse on the main board and it is not blown. Since I have two identical thermostats, I switched them out without any success in getting the system to come on. I checked the voltage coming into my thermostat and it isn't getting any power.

I'm not sure where the transformer is located but will try to locate it. How could I measure the voltage to see if it is working or not? Thanks again, I appreciate the help.