The blower motor is an essential component of any HVAC system. Whenever the system is turned on, it’s the job of the blower motor to help produce warm or cool air. To put it simply, without a well-functioning blower motor, your heating or air-conditioning system will stop working. And while this unit is incredibly durable, regular inspections go a long way toward avoiding sudden failures and extending the life of your equipment.
If your blower does suddenly stop working, it could be a relatively small problem that can be fixed with miscellaneous electric heater parts or a signal that the entire motor needs to be replaced. Here are some helpful tips on how to test and troubleshoot your HVAC motor.
Power Check
Your first step is to check the power source—a simple interruption of the incoming power could be the reason your blower has stopped. If you’ve confirmed the power is functioning, investigate the low-voltage control circuit. Go to the fuse box and see if the circuit breaker is tripped or if a fuse has blown—both signs could point to a short in the motor. If the circuit and fuse appear in good condition, carefully take the panels off the motor. Because HVAC systems are frequently found in dusty areas such as basements or crawl spaces, they have a tendency to get caked with dust and debris, which can cause the motor to short out. Wipe down the surface with a clean rag and power on your HVAC system again to see if this was the culprit. If the motor still isn’t working, it’s time to take a look at the windings.
Windings
When a simple cleaning doesn’t do the trick, you’ll need a multimeter to check for AC voltage directly on the contacts. You’ll also need to check the windings for resistance, which is measured in ohms and could indicate either a short or an open circuit in the motor. If it’s a 120V motor, there should be three or four colored wires along with two brown wires and a white wire. To gauge the resistance, use the multimeter to find the reading between the white wire and each of the colored wires. If the reading is zero, chances are there’s a short in the winding. An infinity reading, which is usually shown as “OL”, or overlimit, on digital multimeters, means there’s an open motor winding. The bad news is, both of those readings indicate that your motor is shot and needs to be replaced.
Capacitor
If the windings appear to be in good shape, your next step is to test the capacitor. This component produces the torque in the blower wheel or fan belt that powers the motor. Some signs of a bad capacitor could include a humming sound, a higher than normal energy bill, or an air conditioner that won’t blow cool air or turns on and off on its own.
The capacitor is usually connected to the two brown wires that extend from the motor. Special capacitor testing tools are available, but if you don’t have one you can check the resistance with a multimeter. If you do have a capacitor tester, the readings are measured in what are known as microfarads and they should be within 10 percent of the component’s rated capacitance, which is the ratio of the change in the electric charge compared with its electric potential. This will show up as a number listed in “uF” or “mfd” and if the number doesn’t match the rating, it’s time to replace the capacitor. If you are using a multimeter to test the capacitor, connect it to each of the terminals. You know the capacitor is functioning properly if the number begins at zero and immediately increases to a much higher number.
When to Replace an HVAC Motor
As mentioned, HVAC blower motors typically have a long lifespan—many experts claim that the average operational life of modern blower motors can extend up to 20-plus years with proper maintenance. So remember to perform regular inspections and keep the area around your unit clean and free of moisture.
If your system does start to falter, follow the recommended steps above before making a service call. In many cases, you might be looking at a simple blown fuse or gunk around the equipment. However, even though blower motors are durable, they don’t last forever. After many years of heavy use, even the toughest and best-designed machinery can start to experience wear and tear and eventually break down. The good news is, compared to replacing your entire furnace or air conditioning system, the cost of a new blower motor is relatively low. In most cases, you’re looking at anywhere from $200 - $300 to just under $1,000, depending on the model and the complexity of your HVAC system.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.