Wiring for Power Window Relays

[John Salla]

I am attaching a diagram of how I have wired the driver side window with relays. The problem is that although the relays are clicking when a ground is applied to pin 85, the windows are not moving. I previously wired power windows and I believe I used the same setup as shown in the attached drawing and the windows went up and down. What am I missing? Do I need to wire pin 87a? Thanks for your help.

John S.

 

[cowboybob]

... Do I need to wire pin 87a? ...

Yes.

 

[John Salla]

Hi Cowboy and thanks for your response. Am I correct that both 87a pins would be attached to ground? Am I correct that in a relay situation for pins 85 and 86 it does NOT matter which one is 12v and which one is ground and similarly for pins 87 and 30 it does not matter which one is 12v in and which one is 12v out?
Thanks so much for your help.
John S.

 

[cowboybob]

... Am I correct that both 87a pins would be attached to ground? ...

Yes.

Just to illustrate (in this case, there is NO 12VDC applied to either relay: Sim is OFF - I don't have a center off SPDT switch component):

You might note that 12VDC is always applied to BOTH terminals of the motor when neither relay is energized. Keep that in mind when playing with the motor.

 

[KeepItSimpleStupid]

A quick note:

A few things are arbitrary. You can have both side of the motor connected to ground or both connected to +12 when teh relays are off.
You can have a closure to ground move the relay or a closure to +12 turn on a relay.

Both relays ON or both relays OFF mean motor stopped and operating into a short (dynamic braking).
A small diode e.g. 1n4001, 1n4002 should go across the relay coil in a way that it doesn't conduct.

The contact numbering has meanings and there are two different pin-outs of the automotive relays. If you follow the numbering scheme, them a relay with an internal diode won;t blow up if used as a replacement.

The installed diodes should go close to the coils. The diodes "protect" any solid state devices driving them.

 

[shokjok]

The motors are idle from the lack of a ground return through the relay, and yes both relays are feeding 12VDC to the motor.
Battery negative isn't shown to be active as circuit ground - simple oversights in the drawing.
cowboybob's schematic lacks a motor ground return, so that circuit won't work for you.

 

[KeepItSimpleStupid]

You might note that 12VDC is always applied to BOTH terminals of the motor when neither relay is energized. Keep that in mind when playing with the motor.

With a little re-arranging, you can have the motor "normally grounded" when it's not in motion. You can also have the relays take +12 or ground to tun them on, again with some re-arranging.