Last night I installed a simple hunter 5/2 programmable thermostat. I carefully reconnected the wires and labeled them. When I put the batteries in and turned it on the fan instantly powered on, but would not stop. I had it turned to heat and it ran all night long. Even when I removed the batteries from the thermostat, the fan continued to run. I had to turn off the breaker in order to get the fan to stop running.

Please advise how to fix this problem.

How do you have it wired?

Is the fan switch on on or auto?

The system is on auto. Even when I disconnect the batteries and the RH wires the fan stays on. I have to cut the power at the breaker in order to get the fan to turn off.

The Hunter people say that it is a broken relay on the heating/cooling unit. But the unit worked yesterday when I had my old thermostat on there. I don't understand why it would be broken or what I could have done to break it by simply rewiring it.

Thank you for your response.

How do I fix a broken relay, and does that sound like what it is to you?

Sorry. I meant to say that even when the switch was set to "off" not auto it remained powered on. Nothing but turning off the breaker will make it stop.

Your relay could be stuck. You can shut the power off at unit and with a screw driver handle tap on it . Sometimes that will free the contacts . If that solves problem I would replace. Not that expensive. If relay is on board most time they are not replaceable but must replace expensive board

Can you explain what to do in a little more detail? I am not sure what you mean.

Thank you.

On newer furnaces, everything is controlled by relays on circuit board. They are little square metal boxes. Sure clue you are looking at a relay if it has a horsepower on it. The circuit board often is often under the cover you remove to get at the filters. The relays are cheap little things prone to stick. A rap with a screwdriver handle often frees them. Unfortunately, they now come attached to a circuit board that requires techs to be trained in CPR when they give the customer the bill.