When an HVAC fan stops spinning, the most common call-out is a “dead motor.” But before you quote your customer for a full motor replacement, it’s worth checking the hum.

The “Hum” Test If the motor is humming but not turning, it’s often a sign that the motor’s windings are fine, but the starting capacitor has failed. In the Queensland heat, capacitors are often the first component to degrade.

How to tell the difference:

• The Capacitor: Look for bulging, leaking oil, or “burnt” terminals. Using a multimeter with a capacitance setting, check if the microfarad (µF) reading matches the label. If it’s more than 10% off, it’s time for a new one.
• The Motor: If the shaft is difficult to turn by hand (with power off!), the bearings have likely seized. If there is a strong smell of burnt lacquer, the internal windings have likely cooked.

Why it matters: Replacing a capacitor is a 10-minute job that costs a fraction of a new motor. However, if the motor is over 10 years old, a failed capacitor is often a “canary in the coal mine” for a failing motor. At Edington Agencies, we stock both high-quality run capacitors and the replacement Fasco or Marathon motors to get the job done in one trip.