proworker

I have a American Standard heat pump unit that will not switch from heat to cool.The thermostat has been replaced. The problem started after the house was struck by lightning. The switching valve will change over if either the orange or blue wire is unplugged. There is 24 volts at the control board and the LED is flashing normal.

kok328

is there 24Volts on the either the blue or orange.
I'm thinking you have a short in one or both of them.

proworker

24 volts on both

kok328

I would think that you would have 24 volts on one or the other but not both. really sounds like a short in the control wire for the switching valve.

Wuzzat?

The most hardy components are things containing coils; solenoids, motors, relays.
The least hardy are electronic components.

I guess you should post a schematic.
In your case it sounds like you can rig a bypass switch and so never have to solve the problem of finding the failed component(s).

proworker

sorry for the misinformation earlier. I have 24 volts on the orange wire not the blue. When I unplug either of them the valve switches. However I ohmed the ambient temp sensor and it is open, could this possibly be causing my problems?

kok328

Sorry, I don't have experience with heat pumps but, now that I think about it, you should have 24volts on both the switching valve and the A/C circuit.
The blue is to run the A/C and the orange would reverse the A/C into heat mode. So yes, it could be the open ambient temp sensor holding out the voltage to the blue A/C wire. As a test, you could bypass the ambient sensor with a piece of wire and see if this allows the A/C to run.

Wuzzat?

Did you try both polarities when you checked it? Diodes can be used as temp. sensors but the wire colors into and out would be different.

Usually the thermistor sensors read lower ohms when hot.