I have a heat pump that seems to be stuck in heat mode. When you try to turn the a/c on it runs heat. I got the a/c to run by cycling the power a couple of times but after having to use the heat again, it is stuck again. Could this be an electrical problem or is it probably the reversing valve?

Its hard to say, could be vavle. I would start at would contols the vavle, thermostat, control board, don't think zebras

What controls the valve

I had this problem before it was a Trane heat pump and the only thing I did was turned power off on the defrost board and turned back on is still running and I haven't had any more problems

The reversing valve is 24 volts controlled by the thermostat and defrost control board. What brand A/C is this?