how does it operate - wiper motor

Discussion in 'Electrical Systems' started by Chuck71RS, Jan 5, 2020.

  1. Chuck71RS

    Chuck71RS Veteran Member Lifetime Gold Member

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    Can someone provide how a 3-prong switch operates a 3-prong wiper motor?

    ---Power comes through the wiper fuse to the motor when key is in run or acc
    ---When circuit is closed, power exits the switch to an external wire going to ground

    ---How does the wire on the middle switch prong control the motor on and speed? (Stuff in the motor lowers voltage for "LO" speed and bypasses for "HI" speed? Does power go from the middle prong to motor or motor to middle prong?)
    ---Where is the circuit opened and closed? (Motor or switch)

    I read the electrical sticky hidden wipers and saw the photo of the uncovered switch but I have no idea what I am looking at. Does not explain how low and hi switch positions speeds up and slows down the motor
     
    Last edited: Jan 5, 2020
  2. hogg

    hogg Veteran Member

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    I may be wrong, but think of it as full power at motor all the time , for fast straight to gnd at switch,one for middle and another for slow speeds going to switch ,each setting at switch uses the same ground,and so does the washer motor,power at washer motor all the time , when switch is pushed it gnds. the washer motor and slids over to gnd. slow speed on wiper motor . I am sure ther is more to it than that . maybe ,I think the middle speed wire and the slow speed wire pick up at different points in the winding of the motor,,,, maybe
     
    Last edited: Jan 6, 2020
  3. dave@ztech

    dave@ztech Veteran Member Lifetime Gold Member

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  4. hogg

    hogg Veteran Member

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    back to top for you
     
  5. Chuck71RS

    Chuck71RS Veteran Member Lifetime Gold Member

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    I found a Youtube video by Double R Restorations bench testing a hidden wiper motor 70-73 with various switches, including the 98. It pretty much filled in the basics of the system. Motor is controlled within the switch by different combinations of grounding at the three switch positions. There is also a switch for parking. He includes a data table of continuity for the four wire connections (including the ground on the side of the switch). Used the mutimeter but did not understand the results. Sent a conversation to Double. Below link to his video
     
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  6. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    Not sure if you ever got it figured out, if not maybe this will help you:

    The 3 terminals next to each other by the round motor are terminals 1, 2, and 3. The middle one is power in and is black and yellow stripped on my car (1970). 1 is the high speed and on the top of the vertical line of 3 terminals when looking at the motor mounted in the car (mine are oriented vertically with terminal 1 on top, terminal 2 in the middle and terminal 3 on bottom; later motors had the terminals horizontal, just think of it as the whole terminal strip rotated counterclockwise a quarter turn; so terminal 1 would be on the left, 2 in the middle and 3 on the right if it’s mounted in a second gen camaro and you’re standing in front of the car looking at the fire wall). The wire to Terminal 1 is black on my car. I already talked about terminal 2, the one in the middle. Terminal 3 is park and is the bottom of the 3 vertical terminals, which is light blue on my car. 4 and 5 are together by the pump. I don’t think their order matters as they are in series (unless a diode was installed on the coil, not likely). 4 is black and yellow stripped and wyed with terminal 2 on a non-delay motor, but basically needs 12v like you get from terminal 2 (terminal 2 and 4 are 12v hot anytime the ignition is on and I think also when it’s in accessory position). Terminal 5 is dark blue on mine and goes to the switch.

    The switch on our cars only varies which combination of wires are grounded completing different circuits. And the grounds are after the motor has power running through it (from terminal 2 for wipers and 4 for washer pump).

    what you also need to understand is that this motor is a “shunt motor” as opposed to a standard dc motor that you are probably familiar with. It’s done like this so you have constant speeds, regardless of load. as opposed to a normal motor that slows down as load goes up (think of drilling a hole in wood, in the beginning with low load it spins fast, as the drill bit goes deeper and has more load, it slows down) That’s why it doesn’t matter if you’re wiping drizzle, heavy rain or snow the speed is fairly constant of your wipers. Otherwise with a normal dc motor, the wiper speed would go down as load increased. Trying to wipe heavy snow and the wipers would barely move. While trying to wipe drizzle and they’d be really fast.

    Also, the speeds are accomplished by changing the flow of electricity through the motor, by changing the grounds.

    Only the center terminal in is power for the wipers (terminal 2). The other two terminals are a ground. Changing the combination of grounds does different things. Power and one ground is high speed; power and the other ground activates the park function. I forget right now the orientation for low speed, I’ll have to check when I get home. I believe it’s both grounds.

    When you switch to park, the ground completes a circuit which activates a solenoid that’s pushes a claw up that grabs the spinning flywheel of the linkage. It disengages it from the normal path which is what pulls the wiper linkage into park. Once they are parked, it will release so when you turn them on, they are normal again.

    if yours aren’t parking, you need to see if the claw on the solenoid is going up. These motors are fairly easy to bench test once you understand the operation.

    It’s important that the body of the wiper motor is grounded!!! Most likely on yours, you are missing the ground strap from the body of the wiper to one of the mounting screws that connects the wiper to the body. And that mounting screws have good clean contact with the car body to complete the ground. Is your car body to chassis and battery to motor ground straps in place? I assume so, otherwise you’d have other issues as well!

    You can pm me if you have more questions. I’ll try to check back once in a while.
     
  7. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    Also, check that your switch is grounded to the car! Earlier switches were grounded by mounting, later switches had a separate ground wire to the metal dash board brace.

    if the motor or switch aren’t grounded right, it won’t function right.
     
  8. JordanZ28

    JordanZ28 New Member

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    Hi there
    Just saw your reply on power trunk can you send a picture of your setup I found a power trunk which is a nos of Buick I am not sure if fit my camaro 78.
    Thanks
     

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