OK, I have an old thermostat that needs to be replaced. Just to be thorough, the old thermostat is a Goodman mod #HPTD18-60. It's a 24v line that controls both heating and cooling and has a multistage heat pump.

The new thermostat is a honeywell RTH7400D. The old thermostat uses the following wires:

Y, COM, R, G, W2, E/W3, O, B

The new thermostat uses R, O/B, Y, G, C, L, E, AUX.

The problem is that the O and B on the new theromstat are on the same connection. It says that if the old thermostat had both an O and B wire then I need to contact honeywell. I did that and got no help. They just said to call someone to install it.

Where should all the old wire go in the new thermostat?

I don't want to spend a service call fee for soething that should not be this hard to install.

Thanks for any advise.

If you didn't get any instructions on the functions of the contacts of the thermostat, I would go back to where you bought it. If they can't help, ask for your money back. I think for what you pay for the more complex thermostats, you are entitled to at least a list of the terminals and their functions.