Crown Victoria V8-4.6L SOHC VIN 6 (1996)
Blower Motor Resistor: Description and Operation
Blower Motor Switch Resistor
The heater blower motor switch resistor (18591) assembly for the Manual Temperature Control (MTC), operates in the following manner:
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The assembly is located in the engine compartment on the A/C evaporator core housing (19A559).
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Three resistance elements are mounted on the resistor board to provide four A/C blower motor speeds.
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Depending on the heater blower motor switch position, series resistance is added or bypassed in the A/C blower motor ground circuit to decrease
or increase A/C blower motor speed.
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An overheating protective device (thermal limiter) prevents heat damage to the A/C evaporator core housing.
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Overheating of the resistor coils can occur when the system airflow is stopped or reduced as a result of the A/C blower wheel (19834) becoming
locked and/or is unable to turn freely.
The heater blower motor switch resistor contains a thermal limiter, which is used as a temperature protecting fuse.
Blower Motor Thermal Limiter
The thermal limiter, used in the heater blower motor switch resistor, performs the following functions:
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It serves as a temperature protecting fuse.
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It is located a predetermined distance away from the resistor coils and in series with the coil circuit.
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It will open the resistor coil circuit when temperature of the thermal limiter reaches 121° C (250° F) interrupting blower motor operation in all
speeds except HI.
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The spring contacts separate when the wax softens, causing an open circuit in the heater blower motor switch resistor.
