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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a model GUK125N20A1 furnace and the fan continuously

Customer Question

I have a model GUK125N20A1 furnace and the fan continuously runs and its cold air. when I shut the thermostat off and then the turn the power off to the furnace wait 2-4 minutes then turn the furnace power back on, and then turn on the thermostat I get heat, but only for the first cycle as soon as the burner turns off the fan continues to run and blows cold air. can you guide me on how to diagnose the root cause
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: the filters are brand new Filtrete filters, and the thermostat is a filtrete 3m-30 I have just purchased the home and I'm trying to get up to speed on everything to I reset the thermostat to factory settings and set it to manual mode to hopefully negate some variables.
JA: Do you plan on doing the work yourself?
Customer: yes I'm an electro-mech engineer and have experience in HVAC but i'm not familiar with this furnace
JA: Anything else we should know to help you best?
Customer: I was suspect that the thermostat was the issue and was going to use a basic thermostat I have to hopefully eliminate it as a possible cause, do you have any suggestions
Submitted: 11 months ago.
Category: HVAC
Customer: replied 11 months ago.
arcoaire, Envro Plus 90 ultra efficient furnace
Expert:  Brian HVAC Guy replied 11 months ago.

Hi I'm Brian and I'm here to help!

Please allow me a moment to review, gather my thoughts and type a response or ask further questions.


Expert:  Brian HVAC Guy replied 11 months ago.

Is your furnace showing a fault code after restoring power and heating for a couple minutes? This sounds like a high temperature limit trip, an induced airflow issue or a flame failure fault. A code would help us narrow this down further.