I woke up this morning to a cool house and a red light on my thermostat. Looking at the furnace, the high pressure indicator is lit. Shutting it down and restarting did not help. Is there anything I can do (as a non-HVAC person) to to resolve this before making a phone call? The furnace is a WaterFurnace, ATV034A110CRT, horizontal loop, one Grundfos pump, and I believe it is all about 20 years old. Thanks in advance.

If you reset it and its still not working... Call a pro, they go into fault for a reason 99% of the time and you don't want to cause any harm by trying to fix it yourself.

I did some further checking, and the high pressure switch is open. That should rule out the control board. If the switch is open due to a true high pressure situation, should the refrigerant pressure equalize through the system if the compressor has not ran for 10-12 hours? If the pressure does in fact equalize, then shouldn't the compressor start and run until an overpressure condition opens the switch again, assuming the switch is good and has not failed in an open state? I am trying to satisfy my own curiosity, as I know I am not a HVAC guy, but I am a controls engineer and understand circuitry.

Some of the diagnostic lights on WFs have a dual or triple purpose. read the legend closely for a second or third cause for that particular light.

dugmick,

We have read your comments in regards to the high pressure light on your unit. Unfortunately, we are unable to determine what the issue might be without more information. We would suggest contacting your WaterFurnace dealer to discuss a resolution. If your dealer is unable to find a resolution, please have them contact our technical support staff for further assistance.

WaterFurnace International, Inc.