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Carrier Gas Furnace Troubleshooting


In this Carrier gas furnace troubleshooting guide you’ll learn what to look for if your furnace won’t come on or isn’t working properly.  Carrier gas furnaces have a very good service record in general but things can go wrong on occasion.  This guide will help you solve the problem quickly if possible or let you know when it’s time to contact a furnace professional for service.

Carrier Gas Furnace Troubleshooting Step by Step

1. Check the Thermostat: Sometimes the thermostat gets turned off or the setting changed by accident.  The truth is, many homeowners have thought their Carrier furnace wasn’t working but all they needed to do was to turn on the system or turn up the heat. This can easily be overlooked.

2. If the system is on is set at a point above the room temperatures, turn the system to fan mode. Check the circuit breaker for the furnace and the on/off switch on the furnace.  If the circuit has been tripped, check the control board of the furnace before resetting the circuit.  If the board has obvious burn marks, indicating electrical malfunction, call for repairs.  Check for obvious loose wiring.  If everything seems to be okay, reset the circuit.

If at this point your Carrier gas furnace isn’t working, the problem is most likely the thermostat, furnace control board, blower motor or the run capacitor. If the thermostat is old or a cheap version, you might consider replacing it to see if that works.  Or you can remove the cover or loosen it from the wall to check for loose or damaged wiring that may indicate the problem.

3. Check the condensate pump, if your furnace has one. If the reservoir is full, then the pump may need to be replaced or the wiring to it tightened.  If the wiring is tight but the pump won’t come on, it probably needs to be replaced.

4. If the furnace has a standing pilot, check to see that it is lit.  If the pilot is lit and is touching the thermocouple, then the thermocouple is very likely your problem. Relight the pilot if it has gone out.

If there’s no pilot light, does the hot surface igniter come on and glow?  If not, it may need to be replaced.

5. Next, listen for the draft inducer motor.  This motor should start before the burner fires.  If it is not running, it may need replacing, or this may indicate a problem with the control board. If it is running but the furnace won’t fire, the flue could be blocked or the limit control might be worn out and need to be replaced.

6. If everything checks out to this point but the burner won’t fire, the problem is likely the gas valve.  It may need to be cleaned or replaced. Make sure the gas line hasn’t been turned off by accident.

7. If the furnace fires but won’t stay lit, the flame sensor may need to be cleaned or replaced, or the furnace control board could be bad. If you’re Carrier gas furnace is a condensing unit – a high efficiency furnace – it may be that the condensate pump is bad or that the trap in the condensate drain is filled with sediment. If the drain trap can be accessed, check for debris and clear any that is found.

8. If the furnace fires, the blower should come on within a few minutes.  If it doesn’t, the motor may be bad or the run capacitor may need to be replaced.


As you walk through this Carrier gas furnace troubleshooting guide, the source of the problem might be identified or at least narrowed down.  You may be able to fix the problem yourself.  If not, call a professional furnace technician.  Your diagnostic work will give you an idea of what may be wrong and will help you discuss the problem with the technician.  The more knowledge you’ve got about the cause of your furnace’s malfunction, the more you’ll be in control of the decision-making about repairs.  You won’t have to simply turn it over to a repairman and hope you aren’t getting ripped off!

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3 thoughts on “Carrier Gas Furnace Troubleshooting

  • January 7, 2013 at 6:52 pm

    After a power outage, my Carrier Gas Furnace blower motor will keep running, long after the burner has go out and cold air is coming out of the registers. I seem to have no control from the wall thermostat. I have to go upstairs to the hallway and unplug the furnace from the outlet to shut off the fan.

    The burner and pilot all seems to work just fine. There appears to be a device (maybe a temperature relay device) that is probably involved in the burner box called a STEMCO 430-1441 and also what looks like the a simple snap-switch, bimetal disc type thing installed more above the fire box where the exhaust goes. I disconnected one side of that switch while the blower was going and it had no effect.

    I would be happy to have any ideas you might have! There is also another controller device Called a Honeywell S8610U involved maybe in this?


  • January 18, 2013 at 1:58 pm

    quick question – when you turn the thermostat up can you get the burner to ignite and blow out heat?

  • February 21, 2013 at 7:57 am

    Yes and No
    It should kick out heat if the system if functioning correctly. It will however only heat at a constant rate….turning it up wont make it get hotter quicker just eventually hotter. If your system is not functioning correctly you may want to examine your flame sensors.

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