ASI's Information Articles


Air Conditioning


Air Conditioning Units

Gas Furnaces

Oil Furnaces

Electric Furnaces

Heat Pumps

Geo Thermal Heat Pumps

Thermostats

Water Heaters


ASI's HVAC Services

Air Conditioner Repairs

Furnace Repairs

Heat Pump Repairs

Maintenance Services


Service Request Links

Request a Service Call

Request a Free Estimate

Request Maintenance Services

Inducer Fan or Blower Sequence

When a gas furnace heating unit has 24 volt power applied to the “W” terminal at the furnace and the negative side of the circuit is present ion the “C” terminal (usually this is wired to ground or some metal part) the unit will start the heating sequence.


Inducer Fan Assembly
The first thing a gas heating furnace does on a newer unit is it starts the inducer fan motor. The inducer fan motor is a small motor usually in the gas burner compartment, this small fan or blower is required to pull the hot gasses through the heat exchanger and it blows those gasses into the flue vent.

This inducer fan motor must be proven to be running properly usually with a safety pressure switch connected to the inducer fan blower housing with a small rubber tube, if the inducer fan motor is not proven on.

At this point the gas furnace heating unit will usually stop the inducer fan motor and may try the same sequence a couple more times after a time delay, if it continues to fail to run the heating unit will usually shut off and lock out.

This an be caused by a faulty pressure switch, a bad rubber tube or in some cases the inducer fan or blower itself is not working correctly or there is some sort of blockage in the gas vent flue.   

Some older gas furnace heating units do not have an inducer fan and are natural draft units, most of these heating units have been replaced but there are a few still out there.

These heating units usually do not have a control board or have a much simpler version of a control board which is usually just a ignition control unit.


Not all Draft Inducer Fan Assemblies look alike, in this example you can see a very simple style of assembly with an open cooling fan in front. This particular assembly was removed from the blower housing and you can now see the blower wheel itself.







CAUTION - Always be very careful with electricity as it can be lethal, if you are not comfortable performing any of these steps please do not perform them, of course you are performing these steps at your own risk.

Important Note: The heating system control board is sometimes very sensitive to static electricity, avoid touching this board to prevent failure.

ASI's Related Articles Gas Heat & Furnaces Cracked Heat Exchangers Furnace Failure #1 Cause Furnace Maintenance Tips Gas Furnace Burner Ignition Gas Furnace Flame Sensor Gas Furnace HSI Ignitor Gas Furnace Inducer Fans Gas Furnace Safety Devices Gas Furnace Spark Ignition Gas Furnace Standing Pilot Gas Furnace Troubleshooting Heating Troubleshooting Heating Repair or Replace Heating Op Cost Comparison Heating Consumer Alerts Two Stage Gas Heat

ASI's HVAC Products Air Conditioning Units Gas Furnaces Oil Furnaces Electric Furnaces Heat Pumps Geo Thermal Heat Pumps Thermostats Water Heaters

ASI's HVAC Services Air Conditioner Repairs Furnace Repairs Heat Pump Repairs Maintenance Services Heating Repair Services