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Heater Blower

(1990 Ford F-150)
in Manila, AR on January 15, 2011
Heater Blower runs only at low unpluged the blower ran direct off battery and it ran on full speed
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Popular Answer
check the fan speed conrol switch to be sure the contacts are good for all speeds if not replace the switch. I f the switch tests got replace the fan speed resistor.
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check the fan speed conrol switch to be sure the contacts are good for all speeds if not replace the switch. I f the switch tests got replace the fan speed resistor.
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on January 15, 2011
I suspect the blower switch. The switch directs power through a stepped resistor, if the blower runs on high when auxillary power is applied, the blower is good. I have also seen the switch knob strip out. Look careful at the inside of the knob to see if it is turning the switch.
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