Most modern or high-efficient furnaces include a draft inducer for improved operation and safety. This small blower unit creates internal air pressure to pull fresh oxygen into the combustion chamber while also expelling exhaust gases. Since a failed draft motor can potentially pose a safety hazard, most furnaces will not run if the draft inducer fails.
Because of this, homeowners often first learn about this component when their furnace will not turn on. If part of the draft inducer system stops your heat from working, it may be due to one of these three potential issues.
1. Bad Pressure Switch
If your furnace has a draft inducer, then it also has a draft pressure switch. This sensor acts as a safety device by measuring the furnace's internal air pressure. Since your draft inducer sucks air through the intake and out the exhaust vent, there should be a consistent negative pressure whenever your furnace is running.
Like your furnace's high-limit switch, the draft pressure switch fails "safe." If the switch isn't working, it will prevent your burner from igniting. This failure can be frustrating, but it's necessary to keep your furnace operating correctly and safely. Replacing the switch should usually repair the problem and allow your burner to ignite.
2. Clogged Exhaust or Intake
Since your burner will not ignite unless the draft inducer can create negative pressure inside the furnace, obstructions can also stop the functioning of the draft system. Clogs in your exhaust vent or the air intake will reduce the draft through the furnace, ultimately preventing the draft pressure switch from triggering. Your burner will not ignite under these conditions as a safety precaution.
Blockages are usually not difficult to repair, but do not check for obstructions until you have turned your furnace off to avoid exposing yourself to harmful exhaust gases. If you cannot find any evident sources of trouble, you may need a professional to evaluate your exhaust vent condition.
3. Failing Inducer Motor
The core of your draft inducer is the motor and blower assembly. Like your furnace's main blower, this unit can wear out and fail over time. Intake and exhaust obstructions can be particularly harsh on the inducer motor since they force it to work especially hard to maintain a draft. Electrical issues, such as a failed start capacitor, can also prevent your draft inducer motor from running.
Since your draft inducer plays a critical role in your furnace's safe operation, you should never ignore problems with it. If you suspect a draft inducer issue is preventing your furnace from running correctly, contact an HVAC technician immediately for an evaluation and furnace repair.