How to make certain a heating and cooling reversing valve is working correctly?

If this is a reversing valve on a heatpump all you need do is to find out if you are getting voltage to the solenoid on the reversing valve. The solenoid is energized in either the heating or cooling mode, depending on the unit and normally receives its voltage from the orange wire from the thermostat.

If you have no voltage to the solenoid in the cooling mode, switch it over to heat. If you still have no voltage, the solenoid or the control board is bad and needs to be replaced. If you have voltage, the valve should make a swooshing noise when the unit is switched from heat to cool/cool to heat. No swoosh, valve is bad.

*First, if there is no voltage to the solenoid, then the problem does not necessarily lie in the solenoid, but from the source of its power: a relay, a control board, etc...

*Second, the statement, "No swoosh, valve is bad" is common terminology used by people who don't completely understand how heat pumps and reversing valves operate. The "swoosh" is the refrigerant rushing sound heard when the slider inside the valve shifts positions. The slider is operated by discharge pressure from the unit's compressor. If the unit is low of refrigerant it might not have enough discharge pressure to make the slider shift, therefore no "swoosh" sound.

A lot of reversing valves and compressors have been needlessly replaced by individuals who don't know what they are doing.