We just purchased a hunter thermostat model 44760 to replace the old thermostat when our a/c went out and it reads no a/c power. We have a trane heat pump. We've also replaced the fuses outside next to our heat pump and nothing is working. I believe our wiring is correct. Can anyone help? Thanks. Also, on our old thermostat the brown wire didn't go to anything. The other colors we have are red, blue, green, orange, white, black, yellow.

Check the transformer. Do you have 24 volts on the secondary side? Check out the "stickey" at the top of this forum for thermostats. You can also jumper R, G&Y at stat. Does the ac run with these jumpered?

I believe it has the 24 volts. I'm not very knowledgeable about jumpers and such. Where would I find the transformer? Thanks.

It sounds like you may either be miswired or you have a loose common. List the old and new wiring connections, maybe we can help...

In your furnace there is 24 volt transformer and powers the brains of your unit...

There will be two wires from furnace to the thermostat ***(find out what color

Of wires come off the red wires on transformer)***they go to R and C in

Thermostat

Now you need to put green on terminal G in the thermostat to run the fan...

This should be a good place to test your work -- put thermostat together

Turn power on to furnace and turn fan to continuous -- fan should run

If you get this far get back to me to go from there -- Does fan run??

Many of the new stats require a connection to common so that the thermostat can be powered. You need to have a wire on (C) and (R) of the thermostat. You should have 24 VAC at all times at these terminals. This is what that error means - 24 VAC is missing

You need to compare the terminals at the furnace and the terminals at the stat with wires used. Sometimes, although rarely, some stupid installer will switch wire colors in the middle of the run.

On newer furnaces there may be an automotive type fuse for the 24 VAC. That should be checked too.

Thanks everyone for the help. I'm sorry for not getting back sooner. We did look at the wiring again and found the blue as the common. And we also made sure that none of the other connections were loose. However, we don't have anything to make sure that we have the 24 volts. We decided to call a technician to come look at our heat pump and let us know what else is wrong. I'll be getting back if I need more advice from everyone. Thanks again.

Thanks again. The technician told us that the problem was the transformer, so we got that replaced. Now it's working again. Thanks for all the info. I learned a lot.