Wiring a thermostat

[Tupelo Pat]

I am installing a Honeywell CT3200A programmable thermostat to replace an old dial type Carrier model. It looks like I have spots for all the wires from the old unit except I can't figure out where the blue wire attaches or if it is used at all. (I am assuming yellow to Y, green to G, red to R, white to W) Please help everything is off and it is getting hot!
Thanks Pat

[Ed Imeduc]

Have to ask what did the blue wire go to on the furnace????

R is power

W is heat

Y is cool

G is Fan

ED ;)

[Tupelo Pat]

Thanks Ed,
The blue wire at the furnace ties in to a thicker blue wire that runs into a transformer type thing that is loosley mounted next to where all the other wires terminate.
Thanks Pat

[Cheech]

Sounds like the blue wire might be the common leg (C) on control power.You can verify this by using a volt meter reading betwen red and blue you should get 24V.Blue and ground should be 0V.

[bronek]

I wired new Honeywell thermostat RTH7400D in to my Carrier heat pump. Blue wire plugs into terminal "C". So far all is working :D . Please use this info.on your own risk.