I have an outside heat pump/ac system with gas furnace. The AC works fine but the heat pump doesn't come on. I understand that the default mode of the reversing valve is heat mode so that says to me that it stays in the energized mode. Could this be a thermostat wiring issue. It's a old non programmable. Is there an easy wiring check to see if it's the problem?
Thanks for your help

It could be the thermostat, reversing valve. Reversing valve seloniod,thermostat wiring etc in case it is not always in the heat pump mode. (some mfg's do not have the units set up to be in the heat mode as default.) Make sure you check the fuses and circuit breakers also.

Thanks for the answer. Unit is an arcoaire. Since air works fuses and breakers are OK? Is there a separate one in unit for heat

If the A/C unit works fine both inside and outside units are powered up OK. If you know for sure the default is that the outside unit is in the heat pump mode all the time and the unit will not run in the heat pump mode then the unit is not being told to run in the heat pump mode at all. A signal is sent from the thermostat to tell the unit to turn on. Since it is always in the heat pump mode to start with there is no extra signal sent to the outside unit.(the extra signal will only be sent if you choose A/C mode). I would start by checking the heat pump signal from the thermostat to the outside unit. You will also have to check the gas furnace area for something called a fossil fuel kit. It will contain a relay that could be causing the problem. Not all furnaces use a fuel kit but I have no idea what you exactly have.