Question re: Electric Wipers
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Laughing Gas
Joined: Jun 2004
Posts: 823
Likes: 4
From: Calais, Vermont
Question re: Electric Wipers
I got a 53 F100 w/ 6 volt positive ground. I cleaned up and re-greased my electric wiper motor. I'm wondering how this thing comes to have two wiper speeds. There are three wires at the motor. There are four at the switch; one is power in, the other three go to the motor. The motor is grounded. There is a non-metallic cylindrical element ( about .125" dia X 1.125" long) wrapped with a spiral twist of thin wire (a resistor?) on an non-metallic plate in the wiper motor transmission. If the motor is grounded, why are three wires needed at the motor? I wired it up to the switch and everything seems to work fine. I'm just wondering how it all works.
Lead Driver
Joined: Jul 2011
Posts: 6,599
Likes: 34
From: Rockingham, VA
I got a 53 F100 w/ 6 volt positive ground. I cleaned up and re-greased my electric wiper motor. I'm wondering how this thing comes to have two wiper speeds. There are three wires at the motor. There are four at the switch; one is power in, the other three go to the motor. The motor is grounded. There is a non-metallic cylindrical element ( about .125" dia X 1.125" long) wrapped with a spiral twist of thin wire (a resistor?) on an non-metallic plate in the wiper motor transmission. If the motor is grounded, why are three wires needed at the motor? I wired it up to the switch and everything seems to work fine. I'm just wondering how it all works.
On the 51 wiper motor, there is a mechanical parking switch operated on each revolution of the wiper assembly. With the dash wiper switch in the OFF position, 6 volts is applied to the two motor leads simultaneously. This cancels out the applied voltage as it is 0 volts difference in potential, so the motor stops. That's how it work, but I hope that makes sense.
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Laughing Gas
Joined: Jun 2004
Posts: 823
Likes: 4
From: Calais, Vermont
I'm pretty slow on grasping some of this. I understand now that one wire from the switch would have to go to the motor where the current from that wire would interrupted when the wiper arms are in their parked position. That non-metallic plate at the wiper motor transmission has a simple electrical contact that opens by a cam on the drive arm at the wiper motor. So, when the switch is turned to off, current is still flowing to that contact until the cam opens it and the motor stops. What makes the motor a two-speed motor? I think that this is probably the same question that I'd be asking about the two-speed fan motor, as well. I should probably go to an internet site on "basic electrical principles for dummies", but since this is related to an old truck, I figured I'd ask here.
Tuned
Joined: Oct 2005
Posts: 400
Likes: 2
From: Arvada, CO
The way the two speed motor works in the the 51-52 trucks is probably same as yours. One wire goes to the armature and the other side of armature is grounded. The armature gets a full 6v in both speeds. You then have two field coils that are wired in series. Full 6v to field coils gives one speed then lower voltage to field coils gives second speed. There is a large resistor mounted between the terminals on the motor that reduce the voltage for the second speed.
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