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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22001
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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Furnace shuts off before reaching temp set on thermostat.

Resolved Question:

Furnace shuts off before reaching temp set on thermostat. Green light on furnace control
panel is blinking 3 times. Is this something than I can fix or do I need to call a have a service person come out?
Submitted: 4 years ago.
Category: HVAC
Expert:  BillyHvac replied 4 years ago.



This is a limit situation. The furnace is running hotter than designed and then shuts down to cool.




furnace too big for the duct work.

dirty filter

dirty ac coil

bad blower or weak blower.


Pretty much anything that restricts air through the furnace.



Customer: replied 4 years ago.
Filter is new.
Furnace is 6 years old and has been running fine.
The blower has been kind of noisy for awhile.
Can I replace the blower myself.
If so, where do I get the parts?
Expert:  BillyHvac replied 4 years ago.

You can get parts from any local Heil or Tempstar dealer and also online.


Have you reached into the squirrel cage with power off and felt inside the fins?



Customer: replied 4 years ago.
The fins have some dust on them.
Expert:  BillyHvac replied 4 years ago.

If the curve of the fin is not concave...and leveled off with dirt.dust,,this drastically cuts airflow. The fins cut through the air instead of scooping.


I would recommend remove the blower and clean first.



Customer: replied 4 years ago.
Also the induce draft motor is making a lot of noise. Could that be contributing to the furnace shutting off too soon?
Expert:  BillyHvac replied 4 years ago.


Not usually but it can keep too much heat in the furnace...commonly this slow flow would fault the pressure switch....but it can be somewhat restricitve and still prove flow.


My bet is still on the main blower or wheel.



BillyHvac and other HVAC Specialists are ready to help you
Customer: replied 4 years ago.
Thanks for your help.

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