two speed wiper question

[neal 66]

had two speed wipers at one point,now only have low.im guesing low goes through a resistor some were? bad switch? all ideas welcome.

[Captainfab]

I'm guessing it's either the switch or the motor. The only thing in between is wires. Have you checked that all the wires are connected, and making good contact?

[ray_mcavoy]

I agree with Captainfab. I'd start by checking the wiring & connectors.

Assuming you have original wiring, there should be 4 different wire colors at the wiper motor:

yellow = +12V feed (goes to both the wiper motor & washer pump solenoid)
light blue = high speed control (goes to the switch)
black = low speed control (goes to the switch)
dark blue = washer control (goes to the switch)

The switch is located on the ground side of the circuit. It grounds the light blue, black, and dark blue wires for the various functions.

With the switch in the low speed position it grounds both the black and light blue wires.

With the switch in the high speed position, it only grounds the light blue wire, leaving the black wire ungrounded. So if the black wire is shorted to ground somewhere else along the way, it will have the same effect as the switch being in the low position.


As a bit of a sidenote, there is a resistor in the circuit but it is part of the motor assembly (not an external inline component). It limits the current through the motor's shunt field winding in high speed. So if that resistor fails (open circuit), no current will flow through the shunt winding, all the current will go through the armature and series field winding, and the motor will actually run too fast on the high speed setting. Low speed operation won't be affected because the black wire (mentioned above) bypasses that resistor to give the shunt winding a direct path to ground.

[neal 66]

thanks guys,havnt gone out to do any wiper investigating but atleast now im armed with some information especialy knowing what wire is for what.just came in from work shop after hand lapping and assembling my vortec heads so atleast something got done.