Question about installing a relay for power windows (on non-pwr win car)

[Tidybuoy]

I'm installing power windows in my '74 and I'm using the factory harness. This did not come with any type of relay. However, I notice on my fuse box cover that it lists a place for the power window relay.

My questions:

I understand the concept of a relay when installing H4's. The power is routed direct from the battery to the lights and the headlight switch is just used as a switching device via the relay.

I don't understand the concept of the relay for power windows. Simply because there is no on/off switch, other than the toggles on the doors. How is the relay for the power windows different from the lights.

Lastly, I have a parts car 914 and it has several spare relays and sockets that are identical parts as the 911. If I were to hook up one of these to my wipers, how would I do that.

Any advice/insight would be greatly appreciated.

Thanks........Vern

[timmy2]

The relay for the windows works in exactly the same way as the headlight relay concept. You use the switches with a low current value running through smaller wiring to activate the relays with a larger current value and larger wiring size to supply the window motors.
This will reduce arcing in the switches making them last longer.

What is your understanding of relay logic and control to wire them up?

[Tidybuoy]

Originally Posted by timmy2

What is your understanding of relay logic and control to wire them up?

That's a funny question

My knowledge is zippo. However, I just installed the headlight relay for the H'4's and so I assume it will be a similar procedure. I will need to take one of the spare relay harness from my parts 914 and examine it and then I will probably have a few questions.

At the moment, I know that my power wire harness (the part that goes to the fuse box) has two wires; a thick red and a brown, which must be a ground. There are also two groups of brown wires along the harness that are brown, connected to each other, with a ground fitting on the end.

From your comments, I assume that the thick red wire is what makes its way to the motors. But looking at the harness, everything ends at a door switch and then secondary wires go from the switch to the motors.

I will look for a schematic to be sure.

Thanks............Vern

[timmy2]

This should help, it's for a '78 and newer but should be very similar.
Shows the relay and wiring.

After viewing this, Change what I said about the use of the relay earlier to:

The relay is used to supply power to the window circuit when ignition is turned on...

The relay and socket would mount in your fuse panel in an empty hole similar to the way your fuel pump relay is mounted.

[Tidybuoy]

Thanks! and Double Thanks.

The chart will work perfect and I'm pretty positive I can follow it. my weekend project has now been assigned.

Vern