Power Window Relays - Danger Will Robinson

[scorpion1110]

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

[chevynut]

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?

[chevynut]

http://chevy.oldcarmanualproject.com/electrical/wiring/index.htm

Look under 55 Chevy for "1955 Electrtic Windows and Seats"

[scorpion1110]

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.

[Rick_L]

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.

[chevynut]

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.

[chevynut]

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.

10396

[scorpion1110]

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

[chevynut]

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.

[55 Rescue Dog]

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.

[scorpion1110]

CN, RD;

So if I dont go with the relay set up, I just split the one 25 amp circuit and feed each side? SPW gave me a diagram to use, but I got sidetracked to the relay discussion.

Sometimes you can overthink these things which I might be doing.

[chevynut]

CN, RD;

So if I dont go with the relay set up, I just split the one 25 amp circuit and feed each side? SPW gave me a diagram to use, but I got sidetracked to the relay discussion.
Sometimes you can overthink these things which I might be doing.

Yes you can power all windows from one source, using one fuse.

As I've said two or three times now :p, whether or not you can do it without relays depends on your switches. One side of the motor needs to be grounded, while the other side gets power or the motor to function. To reverse the motor, that polarity needs to be changed. In order for that to be possible your switches have to switch both power and ground. The original tri5 switches don't do that and you will need relays if you're using them. Again, which switches do you have? Did they come with the power window kit? If they came with the kit I'd wire it the way they recommend. I can't help you anymore without understanding what you're working with. :geek:

I wouldn't worry much about the voltage drop through good relays, so if that's the simplest way to wire them that's how I'd do it. Relays are used all over modern cars for all sorts of functions and they can switch a lot more current than power windows draw. And it's really not hard to troubleshoot problems with them. That said, if you don't need them I wouldn't use them.

Happy New Year! :)

[55 Rescue Dog]

For reference, here is a typical 80's GM power window schematic, which is pretty simple by reversing polarity. Just follow the yellow brick road. With 2 windows it would be the just the right half of the drawing.
10403

[scorpion1110]

CN, RD:

Here is the SPW Schematic:

10407

Based on your thoughts, I am going to wire per their recommendation. The voltage drop wont have a measurable impact so the relays are probably not necessary. If they are I will just pull the kick panels and door panels and wire the relays.

I am definitely over thinking this. Much thanks for the help and the drawings. I think they will be a help if I need to rewire.'

Happy New Year,

S

[55 Rescue Dog]

I can see how it's confusing, since the SPW schematic leaves a lot to imagination. It doesn't show what's inside of anything, other than a couple black boxes with a bunch of terminals. It's just a wiring diagram is all. Just do it their way, and relays wouldn't work anyway with their setup.

[chevynut]

That is an awful wiring diagram. I can't even tell what's the motors and what's the switches. I assume the motors are the things with two leads, but that's a horrible drawing. The switches I assume are the two top things. There's no reason you can't wire in relays if you want to. All you need to do is figure out which terminals on the switches go to +12V when you push them up or down and use those signals in the diagram I posted. Pretty sure you could just cut the wires to the motors and use them as the "switch" wires in my drawing. But I don't know why you'd need relays.

[55 Rescue Dog]

The window motors are simply DC motors, and you just reverse the polarity for up/down. I actually have always preferred manual window cranks, which I even had in my 08 Silverado. Too bad there was never a standard which way to turn the crank for up/down, of which I always try and turn the wrong way.
I wish somebody would come up with a 12 volt PLC (Programmable Logic Controller) to program the functions of a car with a laptop. A thought from years ago. There are millions of machines controlled with 24 volt PLC's, that you can watch, and program every input/output live and make whatever you want happen. How cool would that be?

[scorpion1110]

I ended up installing the PW because the regulators were shot. I figured it was just as easy and about the same cost to install the PW.

You guys have me comfortable on the non-relay wire, plus as CN points out I can always install the relays.

I am going to finish wiring them this weekend and see how they perform.

[chevynut]

I wish somebody would come up with a 12 volt PLC (Programmable Logic Controller)

There's plenty of them available.

https://www.globalspec.com/ds/714/areaspec/power_12v_dc