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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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HEIL FURNACE SOETIMES GOES INTO HIGH BLOWER MODE, OTHER

Customer Question

HEIL FURNACE SOETIMES GOES INTO HIGH BLOWER MODE, OTHER TIMES WILL NOT. IF I LEAVE FURNACE SWITCH OFF FOR COUPLE HOURS, IT WILL FIRE UP WITH NO PROBLEM FOR COUPLE HOURS BUT THNE WILL DO SAME ISSUE. NOTHING BLOCKING OUTLET VENT. RECIRCULATION FAN WORKING FINE.
JA: Did you check the furnace's filters?
Customer: REPLACE EVERY MONTH. THEY ARE 14X20X1.
JA: Do you plan on doing the work yourself?
Customer: IF IT IS RELATIVELY EASY- LOOKING AT BLINKING TROUBLE BULB IT GIVES TWO BLINKS SOMETIMES BUT NOT EVERY TIME
JA: Anything else we should know to help you best?
Customer: RE-CIRC FAN RUNS CONSTANTLY. HIGH SPEED BLOWER WORKS FINE WITH HEAT ON BUT ENTIRE SYSTEM WILL NOT GO INTO THE HEAT MODE CONSISTENTLY-SOMETIMES WORKS FOR FEW HOURS OTHER TIMES WILL NOT
Submitted: 3 months ago.
Category: HVAC
Expert:  Phil replied 3 months ago.

Hello, its an electronic problem, probably with the printed circuit board, and its motor speed control output, especially if your furnace is a variable speed blower type.

Its not something most home owners can repair themselves, let me know about your technical skills in that regard, or tell me which direction you are from the center of the nearest city...I will look for a well rated service outfit for you in that case.

Customer: replied 3 months ago.
As the blower handles the recirculation and then the forced air it is the variable type. As for the printed circuit board, does that board handle the high pressure information. Is it possible that this sensor is shooting a 'no go' signal to the board?
Expert:  Phil replied 3 months ago.

Hello, it is entirely possible that the defective high *temperature cut out switch is sending a signal to the board and that based on that signal, the board is not sending power to the gas valve, and IS sending power to the blower speed control so that it runs and cools off what the board thinks is an over heated furnace.

However that does not account for the intermittent nature of the problem...