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Thread: Power Window Relays - Danger Will Robinson

  1. #1
    Registered Member scorpion1110's Avatar
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    Power Window Relays - Danger Will Robinson

    Help! (CN and WC feel free to bring your electrical expertise to the table)

    I am having a total mental block on this.

    I have Specialty Power Windows (SPW) (Front only) set up in my 55 wagon. There is a switch on the passenger side and a double switch on the driver side to control both windows.

    I have a 25amp open ignition switched circuit on my fuse block. I know I need to run 4 relays - 2 each side- 1 up and 1 down. The relays should be 5 lug. However I cant sort out the wiring. Every schematic I pull wont do what I need; and they seem inconsistent. There is supposedly a GM standard layout, but I cant seem to figure out how to adapt that to my situation.

    I believe that the one circuit should drive all 4 relays since the relays only pull about 3 amps. The problem I am having is how to run the relays to the motors and switches and whether I need to do something different on the driver side since both windows are controlled.

    SPW makes a kit PP-1 - $25 approx times 4 that supposedly will do both windows with a schematic but it seems pricey. I think I could do it for a lot less if I could figure out the schematic.

    Does anyone have anything on this? (I had to detour off of my Hydroboost project for a bit because I got the tailgate and liftgate back from the paint shop. I wanted to get them on the car and wire up the speakers and bumper lights and decided to order the parts to do the dash and doors before I get dirty again.)

    Thanks S
    Scorp

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  2. #2
    Registered Member chevynut's Avatar
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    Are you sure you need to run relays with your switches? I don't think the stock tri5 power window switches used relays. Can't you just use the stock wiring diagram?
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  3. #3
    Registered Member chevynut's Avatar
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    http://chevy.oldcarmanualproject.com...ring/index.htm

    Look under 55 Chevy for "1955 Electrtic Windows and Seats"
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

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    Registered Member scorpion1110's Avatar
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    Youre right, relays arent a requirement. Just in reading, using relays saves wear and tear on the motors. I figured since I was putting in a new after-market harness that I would try and cover all bases.

    I could just wire from the stock diagram that came with the windows.
    Scorp

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    How is a relay going to save "wear and tear" on the motor? I don't get that.

    I do understand that if there's enough voltage drop and enough mechanical friction, the motor will stall.

  6. #6
    Registered Member chevynut's Avatar
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    Relays really just avoid "wear and tear" on the switches, not the motors.

    I just remembered something from my vent window wiring. Most modern window motors have two wires and you reverse polarity on BOTH of them to reverse direction. The early 60's vent motors have two wires, but the case is grounded. You have to send power to ONE wire at a time with the case grounded to the body. In other words, there's an "open" wire and a "close" wire. It took me a while to figure that out. Looking at the link above, it looks like the original window motors work the same way, sot if they do you probably can't use the 55 wiring diagram for your SPW window motors.

    I'm sure the SPW windows operate by reversing the polarity on both leads like my Electric Life window motors. My window switches can't carry much current so I've wired them up to just send signals to a power window controller that has an "auto up/down" feature like new cars. There are no relays involved except inside the controller. The one I'm using is from Autoloc, one for each window. I'm also using it for my electric cutouts.

    It can also be done with relays and I don't think it's that hard. I believe you would wire them up just like power door locks. One question is whether the switches you're using are compatible with the motors. Are you using the original '55 switches? How many terminals do they have?

    If your wiring diagram doesn't work with your switches let me know and I'll try to draw up a wiring diagram with relays.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

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  7. #7
    Registered Member chevynut's Avatar
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    Scorp, I just whipped up this circuit drawing for you. If your switches have 3 terminals, one common and two switched (normally open) this is one way to wire them. This is for the passenger window which is controlled by both switches. For the driver's side, you'd just eliminate the second switch. Two relays per window.

    20191231_001.JPG
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

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    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

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    56 Chevy 210 4-door sedan
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  8. #8
    Registered Member scorpion1110's Avatar
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    Quote Originally Posted by Rick_L View Post
    How is a relay going to save "wear and tear" on the motor? I don't get that.

    I do understand that if there's enough voltage drop and enough mechanical friction, the motor will stall.
    CN, from what I have read the idea is that the motors work harder because they arent getting a full 12V and that causes them to wear out. The relays are supposed to deliver a full 12V and in doing so extend motor life.

    I have seen a few forum posts suggesting this, but dont have direct experience with this.

    Thanks for the diagram. I am looking at it. And know I will have a few questions. thanks for taking the time to put that together.

    S
    Scorp

    Rides:

    1955 Chevy 2-door Wagon
    1967 MGB GT
    1970 Honda Trail 70
    1974 Yamaha 175 Enduro
    2004 Tacoma 4x4

    I lost my best friend on 10/3/2018. Rest in Peace Dear Lucy. I miss you everyday.

  9. #9
    Registered Member chevynut's Avatar
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    I really don't think DC motors have a huge issue with low voltage. Lower voltage means lower current. If they drag mechanically, there's more current and it could burn up the motors.

    If you look at the circuit with the relays you can see it's pretty simple. As shown, with no switches actuated, there is ground on both sides of the motor through the relay contacts. All the relays do is switch one side of the motor to +12V while the other side stays at ground. This is the circuit you need if your switches are 3-terminal type as I drew them.

    Some switches have more terminals so one set of contacts can be grounded and the relays can be eliminated if the switches are wired correctly. It depends on which switches you have.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  10. #10
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    Every relay connection, and contact is going to be a potential voltage drop too, plus harder to troubleshoot. It's only intermittent operation, so skip the relays, and just use good switches.

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