Problem: My heat pump is making a funny hissing noise. It sounds like the reversing valve is not working. How does a reversing valve work?
Answer: Yes, if your heat pump reversing valve is not shifting or is stuck in between the heating and cooling mode then you heat pump will make a funny hissing sound or not sound normal. A heat pump which is low on refrigerant charge or has a stuck reversing valve can cause this problem. Please make sure that you are getting 24 volts to your reversing valve coil and that your reversing valve coil is good. If your reversing valve is stuck I would suggest that you check or have your heat pump system refrigerant charge checked. Sometimes when I was doing service I would try to connect and disconnect the orange wire (this is the wire that most of the time controls the reversing valve) and see if the valve shifts. Sometimes a light tap with a rubber mallet on the valve can get the valve to unstick. Make sure you do not dent the valve because a dent will make the reversing valve stick even more. FYI: Many people and service techs, including myself have a hard time diagnosing the difference between a stuck reversing valve and a blown valve on a compressor. The sound the unit makes with a blown valve on the compressor and a stuck reversing valve are real similar. Below we have a YouTube video made by Supercool Slide Rule which shows how to test a reversing valve coil. Below we also have another real good informative YouTube video made by grayfurnaceman which explains how a reversing valve operates. Thanks to Supercool Slide Rule and grayfurnaceman for making these informativ video! If a reversing valve is stuck most of the time it requires replacing the reversing valve. If you have any other questions please feel free to email us: firstname.lastname@example.org or comment below. Hope you have a nice day! We would love to help you out and have your business!