Restore multiple speeds to your auto heater/air conditioner blower by replacing a resistor module. It's a simple, quick change-out.
By the DIY experts of The Family Handyman Magazine
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Restore multiple speeds to your heater blower motor
Resistor module replacement
Remove the electrical connector, retaining screws and the old resistor module. Swap in the new part and reinstall the screws and connector.
Most car manufacturers use a series of resistors to make the heater blower motor run at different speeds. And when one or more of these resistors burn out, you’re usually left with only one heater blower motor speedhigh. The resistor module is easy and inexpensive to replace. It’s then typically installed in the ductwork, near the car blowereither under the dash or under the hood. (Refer to a service manual to locate yours.)