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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22421
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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My gas furnace keeps shutting off before reaching set temp

Resolved Question:

My gas furnace keeps shutting off and turning on even though it has not reached the temp set on the thermostat.

Submitted: 7 years ago.
Category: HVAC
Expert:  BillyHvac replied 7 years ago.

Is the filter clean?

What make /model furnace?

Is there a blinking light in the furnace?

Customer: replied 7 years ago.

I do not know if the filter is clean, it is a Lennox Pulse furnace and I cannot find a model number. I know my husband replaced the filter this past summer.

Expert:  BillyHvac replied 7 years ago.

The number one reason for a furnace to do as you described is to run over down...start again...over down etc.

Before we go further I would strongly recommend checking the filter.

Customer: replied 7 years ago.

I cannot figure out where the filter is--can you tell me how to find it?

Expert:  BillyHvac replied 7 years ago.

What floor of the home is the furnace on?

Attic, basement etc?

Customer: replied 7 years ago.


Expert:  BillyHvac replied 7 years ago.

Thank you. Usually it is on side or the other at the bottom section. Here is a basic layout to look at. Here it is the left side bottom,

Customer: replied 7 years ago.

Okay, I changed the filter, although I didn't think the old one was that dirty. Do you think the filter is the problem?

Expert:  BillyHvac replied 7 years ago.

I honestly do not know...I eliminate the items that pertain to that description.

The Lennox Pulse has a concealed spark plug and sensor so I will not be asking you to get too involved.

Another item is the drain off the furnace. This is a high efficiency furnace so it drains water. If the drains get backed up and stall water in the furnace, it can also fault operation. This involves seeing where the drain comes out and drains to...and seeing if it is clear. Sometimes involves removing drain line from furnace to check.

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