Okay, here we go… I have a 1968 Standard Mercury Cougar. I pulled the dash out for painting and to replace the bulbs. What I found in the harness is an odd single GREEN wire. It was not attached to anything when I pulled the cluster. Okay, so what is it for? Was it meant for use for some kind of extra option that my car didn’t get? Maybe it’s for a seat belt light that my car did not come with. If anybody knows, I appreciate your help.
Bret I have the dash out of my 68 standard and I don’t remember that wire on my cluster. I will check later on and see if it is there. I believe you might be on to something with about an option wire. Maybe even the emergency brake “light on” light that was mounted on the lower portion of the dashboard. Maybe it’s for forwarding thinking people that converted their 68 Cougar’s to convertibles and it’s for the “top switch”, so my Cougar should have it also. 
Steven
Now that is funny! I got my laugh for the day. 
Am I right that this wire has a male bullet on it? That’s unusual, as that means it is for something that this wire is receiving a signal (remember, only female connectors are energized when hot!). So something on the dash cluster would be providing a signal to the underdash harness…most unusual. Can you find its position on the dash cluster connector? That will help folks like me to track it down in the schematics.
Yes, it does have a male bullet on the end. I will check on the cluster connector and get back with you.
It looks like is 3rd on the left from the top/bottom. Depending on how you look at it. There is a green/black on the 2nd position and white/yellow on the 4th position. Something else to consider is that the wiring harness or even the the dash cluster itself may be from a 67 Cougar. A good portion of the interior is from a 67. Door panels, seats, center console, etc. There is no telling at this point. Unable to submit photo for some reason but you have the info that you need. Thanks.
That green wire is suppose to be connected to a a female plug bolted to the back of the speedometer housing as a ground
Now we’re getting somewhere! As you can see in my photo there is no female ground on the back of my speedometer. Would you happen to have a photo of where it is supposed to be? Maybe I can fabricate something to use.
You are missing the copper female plug that should be bolted under the nut holding the voltage reg on, you could cut the plug off and crimp on a ring terminal and do it that way.
The female ‘connector’ is attached to the cluster on the same stud as the IVR.
Here is a picture of the wire and copper connector.
If you need that piece PM me and I can mail one to you.
After looking closer at your picture you can see where the copper plug has been broken off and a piece is still under the nut,
You are absolutely correct! Part of the original piece remains. Thanks guys for so much help! TheRktmn is going to set me up with the piece that I need. Problem solved!
And that dear readers is why the forum exists. In the future, after Google indexes this, some one will search for Cougar dash green wire and this thread will pop up. They will come here, and find the answer and be amazed at what is available out there.
This is true! My issue was taken care of in less than 24 hours. I was uncertain if it would be taken care of any time soon. Kudos to the Cougar Community for stepping up!
That’s what I got as well. What threw me off was the color of the wire, as it should be black and not green. Going back to the original picture of the back of the dash cluster, there is no connection to the grounding lug of the IVR. I have one or two of those lugs as well if Rktmn can’t find his.
Oh, and that does look like a 68 harness.
What else do I need? I thought I only needed the copper female connector to bolt to the IVR. Do you have a pic of what the the back of the dash is supposed to look like?
That’s all you need, and no, I don’t have any pictures.
Sounds good. TheRktmn is helping me. Thanks for looking out too.
Thanks! Mine looks like that now. What are the chances of the IVR going bad? I still have no dash lights. I replaced the fuse, headlight switch and all the dash bulbs. I’m puzzled. 