I need help with the strange electric window regulator

[torbsim]

And every day it's Groundhog Day!

Currently, I have the problem that my Mustang's 73 power windows only work partially or not at all.

There are moments when they behave completely 'normally' and ensure that the windows open and close.

But in most cases, nothing happens! I have already found out that everything in the Mustang is controlled from the central control unit on the passenger side.

I have also checked the voltage and the flow at the terminal in the engine compartment and at the relay.

Current is flowing and there is an audible and tactile click when you turn on the ignition.

Now, I sometimes get between 8 and 12 volts when I measure the purple wire and the contact from the relay.

When I then press the switch, I get a full 12 volts as long as I press the button.

With the blue wire on the relay, nothing happens.

Neither when the button is pressed nor when the button is not pressed.

I'm a little at a loss and actually want to install the door panels, but I would hate to have to take everything apart again.

Do you have any advice or similar experiences, and how did you fix it?

I also recorded a video about the behavior, I apologize for the poor quality, and thanks for your support!

!Watch the Video!

(For better understanding, the right is the purple wire, the left is the blue wire at the safety relay in the video)

Appreciate your help, as always
Ben

 

[Hemikiller]

You need to check between the individual terminals and a ground, your current test method is reading voltage across the relay terminals.

Be sure the relay is properly grounded, it won't work if it isn't. The factory used a #8 external tooth lockwasher between the relay and the shock tower.

The relay is supplied power full time by the Black w/Yellow dots power lead from the starter solenoid. The Purple wire is the trigger, it should have 12V only with the key in Run or Accy. The Blue is the power feed out of the relay to the driver's control panel.

When you turn the key on, the relay will activate. It has a rather unique "click" sound to it, or at least my cars do. I don't hear it in your video. You should also feel it click. It's possible you have the purple and blue wires backwards. I don't have my XR7 here to verify wire placement and the wiring diagram is awfully vague. I would use a jumper to apply 12V to each of the two terminals. If it's grounded properly, you should feel/hear it activate on one of the terminals, that's the one the Purple wire goes to.

 

[torbsim]

You need to check between the individual terminals and a ground, your current test method is reading voltage across the relay terminals.

Be sure the relay is properly grounded, it won't work if it isn't. The factory used a #8 external tooth lockwasher between the relay and the shock tower.

The relay is supplied power full time by the Black w/Yellow dots power lead from the starter solenoid. The Purple wire is the trigger, it should have 12V only with the key in Run or Accy. The Blue is the power feed out of the relay to the driver's control panel.

When you turn the key on, the relay will activate. It has a rather unique "click" sound to it, or at least my cars do. I don't hear it in your video. You should also feel it click. It's possible you have the purple and blue wires backwards. I don't have my XR7 here to verify wire placement and the wiring diagram is awfully vague. I would use a jumper to apply 12V to each of the two terminals. If it's grounded properly, you should feel/hear it activate on one of the terminals, that's the one the Purple wire goes to.

Thanks, @Hemikiller . The clicking sound is there, and it also vibrates a bit when I start the car. The wires should be correct, I've seen in other videos that the purple wire is on the left side and the blue wire is on the right side of the relay when standing in front of it. I will check the ground asap, thanks for your detailed advice as always.

PS: The Cougar XR-7 is a beautiful car and is also on my list!

 

[torbsim]

So, a short update. We tested all the connections and bridged the relay. It makes the clicking noises and also reacts to the ignition, but only 0.8 volts are actual 12 volts come through when the ignition is activated. I now assume the relay is defective and am I organizing a brand new one. When the relay is bridged, all the windows work perfectly! Which makes me thrilled.

 

[Hemikiller]

You might be able to fix the relay you have. The internal contacts are likely burned or corroded, so if you desolder the ground connection and pry back the four locking tabs, you'll have access to the internals.

 

[torbsim]

This is the way. Thanks @Hemikiller