How to Troubleshoot Furnace Blower Motors

Autumn is the time of year when you should be servicing your furnace. If you notice that your blower is not working properly, there are a couple of steps you can take before calling the repairman. Learn how to troubleshoot furnace blower motors and possibly save yourself some money in the process.

Things You'll Need

• Screwdriver
• Volt-ohm meter
• 3-IN-ONE oil
• Needle-nose pliers

Instructions

1. Turn off the power to the furnace at the circuit-breaker box. Remove the blower cover panel from the furnace housing by removing the screws and lifting the panel out.

2. Locate the blower fan wheel and attempt to spin it by hand. It should spin freely with almost no effort. There are ports located close to the motor and blower fan. Add a few drops of 3-IN-ONE oil to the ports and if the blower still does not move freely, then replace the blower motor.

3. If the blower fan does move freely, feel the motor to see if it is hot. If so, allow the motor to cool and inspect the wire connections to make sure they are secure and unbroken.

4. Inspect the capacitor that is located beside the blower--it is a square box with two wires attached to it. If the capacitor is bulging or has oil leaking from it, then the capacitor needs to be replaced.

5. Remove the wires from the capacitor by using needle-nose pliers and pulling the wire leads off of the capacitor terminals. Set a volt-ohm meter to the voltage setting and touch one probe to each of the terminals on the capacitor. You should see a reading of zero that goes to the maximum capacity rating printed on the capacitor. If it does not, replace the capacitor.

6. Turn the power back on to the furnace if the capacitor was replaced. Set the thermostat so that the furnace will turn on. If the motor still does not operate, replace the motor.

Tips & Warnings

• Always disconnect power before servicing electrical appliances.

References

• Troubleshooting
• Test Capacitor
• Motor Replacement