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Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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My furnace stopped working.

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Furnace stopped working. I changed the air filter which was very dirty. Furnace started for a while, shut down again. What are possible problems and solutions?


Hello, I will do my best to help you today.

It could be any number of things. Did you get a blink code on the furnace control board telling you what the failure causes was when the furnace shut down.

When the furnace "shut down" Did the burners just go off and the blower kept running, did the entire system just stop, did it try to cycle back on or did it have to be reset by you? When you changed the filter did it seem to stay on longer? How cold is it where you are? Can you find a furnace model number for me?

JACUSTOMER-ukvlpfdi- :
I will try to restart it and get those answers for you. It is 5 degrees outside but we have a fireplace that is working well.

Matthew :
A 90% furnace condenses the gas and produces water so sometimes this water can cause havoc when the outside temperature drop this low. I don't know where you are located but in places where these cold of temps are not common the installers sometimes do things that are not wise. you need to check your drain line and make sure it isn't frozen or restricted. Check your exhaust and make sure there is no dips or traps in it that can collect water and allow it to freeze in the pipe. All of these things will give you the open pressure switch blink code and cause the furnace to drop out.

If the filter was that dirty it is possible your evaporator coil is also dirty. If anything is causing the airflow on the system to be restricted you will get the open limit circuit fault code and the blower will run until the limit resets. This limit senses the temperature inside the furnace and if the heat isn't being pushed out sufficiently it will open. Dirty filter, dirty evaporator coil, blocked returns, blocked supply runs, malfunctioning blower motor, dirty secondary heat exchanger, or simply a malfunctioning limit will all cause this.

JACUSTOMER-ukvlpfdi- :
Thank you! The tips were great. The furnace is up and running again!

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