Hi. I'm trying to install a programmable thermastat and the directions say to mark the wires before taking them off the old one. They are not marked at all anywhere. I have a red and a white one. Any idea what I should mark them as? Any help would be so appreciated. The electrition I called wants $130.00 to install it for me.

Glad you had the good sense to post here. The red wire, hot from the transformer, goes on R or RH. The white wire to the gas valve or whatever, goes on W or W1. If the new thermostat doesn't have R or W, pick through its instructions and see if it says how the hot and gas valve terminals are marked. Some thermostats need a third wire from the common side of the transformer to a B or C terminal.

If this doesn't do it, post back with details, and I will try again.

Perfect. Just what I was looking for, a life saver. Thanks.