Diagnosing a faulty HVAC blower motor can be a difficult endeavor. The blower motors are the unknown, uncelebrated heart of an HVAC system unit.
Diagnosing a faulty HVAC blower motor can be a difficult endeavor. The blower motors are the unknown, uncelebrated heart of an HVAC system unit. Although they are durable and long-lasting, they still need periodic maintenance. In this blog, we’ll give you some tips on how to diagnose a faulty HVAC blower motor.
Check the Power Supply and Windings
The first step is to check on the health of the power supply. Like motors in cars or washing machines, the blower motor in an HVAC can blow out and fail as well. Look for proper amounts of voltage. This is achieved by examining the transformer. If the transformer or circuit breakers have failed, it’s time to look at the windings.
Let’s look at the windings next. Measure the ohms that the unit is expelling. An ohm is a unit of measurement for electrical resistance. A device known as an ohmmeter will help you. If the blower has a 120 volt motor, then three or four colored wires will be part of the assembly. These wires are what you check the ohms for. The most common colors for these wires would be black, red, yellow, and blue. There will also be a white wire and two brown wires. These secondary wires help you perform resistance checks. Resistance checks give a solid data reading, numbers you can see. When you perform the resistance check, compare the numbers from the white wire and the colored wires. How will you know to replace the motor? If you see a zero reading or an infinity symbol: zero represents a shorted-out motor winding, and an infinity symbol represents an open motor winding.
Mind the Capacitors
Just because the blower motor is not running doesn’t mean it has failed. The two brown wires mentioned above plug into the capacitor. Capacitors help the motor run with more torque. More torque means more fan speed and power. The blower wheel and fan belt need sufficient torque to turn on. If they don’t turn on, the motor doesn’t turn on either. Be sure to discharge the capacitor before it is tested. A tool known as a capacitor tester will help you get accurate readings. Mind the microfarad reading, and ensure that it is within 10% of the so-called rated capacitance on the capacitor. If the readings don’t match up with the rating, then it is time to replace the capacitor. Lastly, remember to keep everything clean.
Crockett Facilities Can Help!
Crockett Facilities Services, Inc. (CFSI) is committed to helping building owners, property managers, engineers, and facility professionals lower their operating expenses through HVAC preventive maintenance. We can develop a cost-effective, customized preventive maintenance plan for your commercial building that will provide you with peace of mind, improved comfort, and energy savings.
To learn more about the importance of HVAC Preventive Maintenance, please contact us at 202.600.2787 or sales@crockett-facilities.com. Our PM contract customers receive priority service with 24/7 emergency service in Maryland, Virginia and Washington, DC.