Want to know how to wire up a 1970's (I'm assuming because that's how old the house is and how old the furnace looks) Carrier Furnace. Here is my wiring at the furnace and I want to know which wires to hook up to which terminals on the Thermostat. These are the wires that run from the tstat to the Furnace:

1. White wire goes to one of two screw terminals on transformer. Other screw terminal on transformer has a blue wire going to gas valve.

2. Blue wire from tstat goes to terminal on gas valve. (so 2 blue wires hooked to gas valve, one from transformer and this one. They each go to different terminals)

3. Red wire from tstat hooks to a red wire that goes to A/C unit.

4. Yellow wire from tstat hooks to a blue wire that goes to A/C unit.

5. Green wire from tstat goes into a metal box on furnace about 4'' by 7''. Also from this box comes a white wire that goes to the A/C unit.

It is wired to an old honeywell round mercury thermostat and on that tstat all those wires go to color coded terminals that match the wires that go to them. (each terminal is not only colored but labeled with the first letter of the color of the wire)


Anyone help me out with wiring the new tstat?? Please and thank you.

Please look in the condensing unit (outdoor unit ) and see if you have a transformer there, this will make a big difference as to how you wire the thermostat.