Hi:

I have a Carrier Weather Maker Infinity gas furnace model # 58MVP120.

The problem is on some occasions the furnace will not switch into full heat mode. The blower seems to gain speed as it it is going to change into high speed but it shuts down before it gets there. Turning off the power for a minute seems to resolve the situation at least temporarily.

I opened the front and interpeted the flashing light to read code # 31. It reads " High heat pressure switch or relay did not close or reopened. Control may be defective or a gas valve is miswired." The furnace has been working well for over five years so I do not believe that it is miswired.

To resolve this myself I have changed the batteries in the thermostat which I thought worked... but it was not the cause.

Any help with this situation would be greatly appreciated. Thank you.

XPrime99

Any helpers?

Sounds like you have a pressure swtch problem. Could be caused by a few different things. Here are a couple of simple checks. Check drain hoses and ports to make sure they are not plugged, check exhaust and intake venting to make sure they are not blocked, check pressure switch hose and port to make sure its not plugged. Also high winds can cause pressure switch problems. These are a few things you can check yourself, other than that, you may need a pro hvac tech in to diagnose system.. as it could be a draft inducer problem, fualty pressure switch etc. Please let us know what you find.

Thanks for the tips.

I have checked ventilation and all seems well. The pump is carrying the condensate water away along with the humidifyer water.

I am not sure what a pressure switch hose is?

I think it is time to call a pro. I will follow up after the fix... to satisfy your curiosity and for any others that may run into the same problem!