As a brief reminder, if your HVAC system is covered by a warranty, be sure to adhere to all criteria to maintain it.

We will walk you through the stages of a gas-forced air furnace and discuss typical issues and their solutions. These are intended to be simple remedies that you can perform as a homeowner, with a basic process you can follow that is not exhaustive of all possible furnace problems. If you are still puzzled after reviewing this list, it is likely time to see a specialist.

HVAC Fundamentals: Troubleshooting the Furnace



The thermostat activates the heat inducer motor, which ignites the gas in the furnace. The furnace forces hot air into ducts.

Step 1: The thermostat requests heat

The heating cycle begins with the thermostat requesting heat. This can occur if the system is set on HEAT when the ambient temperature is lower than the heat setting or if the temperature dips one degree below the heat setting during regular operation.

What Should Occur: When your thermostat calls for heat, a sequence of events should occur at your furnace. If you don't hear a little motor start-up (this is the motor for the draft inducer) or if you don't hear anything at all, there is a problem.

Frequent Problems:

• The furnace does not receive power.
• The thermostat is not communicating with the furnace.

Common Solutions:

• Verify that your furnace has power by inspecting the circuit breaker and any power-off controls located on the unit.
• Confirm that the thermostat is set to HEAT and is at least one-degree colder than the surrounding temperature (go to 5 degrees cooler to be safe for the check). If your thermostat isn't hardwired, you should try again after replacing the batteries. Finally, you can remove the thermostat's front cover and replace it to ensure that the connections are correctly seated.

Step 2: The Draft Inducer Motor Is Activated

If the thermostat and power issues have been ruled out, then you can proceed to the draft inducer motor. This is the motor responsible for drawing air and fuel into the combustion chamber and expelling combustion exhaust gases from home.

What Should Occur: The draft inducer motor should begin to rotate, bringing fresh air into the combustion chamber and expelling air through the vent pipe.

Frequent Problems:

• The draft inducer motor is inoperable. There could be a click followed by nothing else.
• The motor begins to spin, then stops, and nothing further occurs. This may be due to a clogged or defective pressure switch.
• A spinning motor that suddenly stops could also be caused by a clogged exhaust pipe.

Now that there are several potential causes of the problem, finding a solution becomes more difficult. However, the majority of furnaces include an LED status and error code light. You can see the motherboard when you are performing system maintenance and cleaning. The LED is often located on the motherboard, and there is a small window into it on the device.

When all is well, this light should be solid red. However, a list of all the codes is located on the panel's outside. This should be the first place you seek to narrow down the issue. Then, it can be cross-referenced with error codes.