Test the blower motor’s thermal overload by isolating power and checking continuity between the common and each hot lead.

Start by turning off and locking out the circuit to ensure no power is present. Remove the blower access panel and locate the motor terminal block so you can identify the common and the two run or speed leads. Use a digital multimeter set to the resistance or continuity function and place one probe on the common terminal and the other on a hot terminal; a low ohm reading indicates intact windings and that the overload is not open. If the meter reads open loop or infinite resistance between common and a hot lead that corresponds to the affected speed the thermal overload is likely tripped or the winding is open. Allow the motor to cool fully for a minimum of thirty minutes and then retest continuity; many thermal overloads are automatic and will reset when cooled. If the overload does not reset after cooling and proper resistance remains open the overload mechanism or the motor is faulty and you should replace the blower motor assembly.

Three common mistakes are testing with power applied which risks shock and false readings so always deenergize and verify absence of voltage before resistance checks; another is misidentifying terminals so confirm wiring diagrams or mark leads before disconnecting to avoid incorrect measurements; lastly many people assume an open overload is the only cause when a bad capacitor or intermittent winding may cause similar symptoms so perform a full motor assessment including insulation resistance testing with a megohmmeter or checking the start device if applicable. For each issue verify power is off then recheck with the correct test tool, label or photograph wiring before disconnecting, and perform additional motor diagnostics if resistance checks are inconclusive.

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