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Recently I lost the capability to adjust the fan speed on my heat/ac blower. I now only have either off or high. Nothing in between. Do you think it is a bad blower motor or somethin gwith the controls? It is on a 93 F-150.
It's not the blower motor if full speed works. Ford's blowers are simple DC motors. They use dropping resistors, usually inside the air plenum, to supply a lower voltage when the controls are set for less than full speed.
Oftentimes the connections to the resistors get corroded and a simple emery paper cleanup will get things going.
Or the controls or wiring might have an open circuit.
Hi,
i think it´s the switch, because the blower motor, works ... it is just the adjustment switch.
Remove the ****, then the electrical connector of the back, loosen the screws and you can replace the switch.
Look on the outside (under the hood) of the heat/AC box on the firewall. You will see the motor and beside it and below the motor will be a 3 wire plug. This is a resistor that controls the speed. One side is most likely bad. Poll the plus and remove the resistor by removing the 2 screws and see if one side is bad. It will be obvious! The switchs do fail but not as often as the resistor.
That was it! I pulled out the resistor and one terminal was melted right off. Looks like I will be off to the salvage yard to get a new wire harness/connector to splice in. The connector was melted and very difficult to remove. THanks! It will be nice to finally have control of my heat, since winter is coming!
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