Q: Heater/ac blower resistor

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The fan (blower) sometimes works and sometimes does not work. When I jiggle, the wire cable connection to the resistor, the blower will go on sometimes. Is my problem most likely with the wiring, connection, or the resistor itself? And, how would I find out for sure? Thanks.

My car has 44000 miles.
My car has an automatic transmission.

This may be either the resistor or the wiring connection to the resistor. i would recommend first eliminating or confirming the resistor as the problem since this is much easier to test than faulty wiring. Many blower resistors control current to the blower motor in all speeds except high. In high speed the resistor is bypassed and power is fed to the motor directly from the switch. The resistor itself can be tested by doing the following:

Place one lead of the Ohmmeter on terminal 1 of the resistor. Place the other lead on terminal 2 and check against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 2 to terminal 3 and check this reading against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 3 to terminal 4 and check this reading against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced.

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