Reversing Valve
What about the RV?
How it works
A reversing valve is not an overly complicated part. In order to troubleshoot it, however, you must know how it works. If you look closely, on the front by the solenoid valve you will see a miniature reversing valve. This is crucial to its operation. When the solenoid clicks, it redirects high pressure gas from the compressor discharge line (the smaller lone tube on the bottom) and directs it to one side of the valve body via small capillary tubes. Of course you couldn’t achieve any movement if the other end of the body didn’t drop its pressure. The other end is now exposed to the lower pressure via the common suction line that leads back to the accumulator or compressor.
It is this pressure differential that allows the slide assembly inside the reversing valve to move. When it does move, it redirects the high side discharge pressure into one of the outer tubes on top of the valve. The slide assembly contains a u-bend for the other two. This allows the suction gas a path back to the compressor. That said, the solenoid valve does not directly move the slide, it redirects gas to force the slide assembly to move.
The Solenoid valve is an electromagnetic coil. When we power the solenoid, it magnetically pulls on the small pilot valve to direct the gas as we talked about. Some manufactures power the reversing valve in cooling mode which means if the solenoid fails, they are stuck in heat mode. Enjoy that in July. We power the reversing valve in heat mode. If for some reason you lose the solenoid, you get to keep cooling. At least if it happens in January, you still have back up heat. Enough about that.
Troubleshooting the Reversing Valve
The EcoNet VSODC control board includes the defrost logic and controls the solenoid valve.
If for some reason the valve does not function, it’s time to do a little electrical troubleshooting. If the system is in heat mode, does the solenoid click? If not, find where the leads to the solenoid attach to the VSODC and check for 24 Volts AC. If you have power there, but no response from the valve, remove the power and then the solenoid from the valve body. Stick something like a screwdriver or bolt inside the solenoid and connect the wires to a known 24V. Does it engage the magnet? If not, you simply have a bad solenoid. If you check the resistance of the solenoid, it is probably open. If it does engage the magnet, then you may have a reversing valve or pilot valve that is mechanically stuck.
If there is no 24V in heat mode, an h or H displayed on the VSODU, then check the VSODC onboard fuse.
Keep in mind, in order for the valve to shift, there needs to be enough mass flow and a pressure differential between the high side and low side. Some techs and homeowners have heard the compressor at start up make a funny sound. It’s been described to sound like a baseball card in the spokes of a bicycle. It will often go away within a few seconds. This sound is because at start up, there is not enough pressure differential or mass flow to shift the valve. Once the compressor winds up, and creates this flow and differential, the scrolls will set and the valve will shift.
During operation a technician can measure the temperature of the two cold lines. (One coming from the acting evaporator, and the true suction line returning to the compressor.) There should be less than 8-10 degree difference between the two. Any more than that and there may be some leakage from high to low.
If the high side hot gas were leaking into the suction, the true suction line temperature would be elevated more than 8-10 degrees than the suction line leading into the valve.
