Blower motors are regulated by group of resistors that cause the voltage to reduce at different amounts resulting in high to low speeds on the fan. When this fails the motors goes to high speed all the time. These are not expensive or hard to replace. Usually a plug connector and a couple of screws and around $25 will do it. These are located under the dash in the main body of the heater as they rely on air blowing over them to reduce the heat created by the resistance. the side opposite the connector will look like sifferent sizes of wire wound much like a spring to create resistance and slow the blower motor down. Once you have this out you can go to a parts store and ask for a replacement one. good luck
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Blower motors are regulated by group of resistors that cause the voltage to reduce at different amounts resulting in high to low speeds on the fan. When this fails the motors goes to high speed all the time. These are not expensive or hard to replace. Usually a plug connector and a couple of screws and around $25 will do it. These are located under the dash in the main body of the heater as they rely on air blowing over them to reduce the heat created by the resistance. the side opposite the connector will look like sifferent sizes of wire wound much like a spring to create resistance and slow the blower motor down. Once you have this out you can go to a parts store and ask for a replacement one. good luck