The drivers side cable for the remote mirror has broken inside the door. This is the squarish chrome style, not the "bullet" or sport mirrors. Picked up a used mirror and cable assy, cable is good but the chrome on the head is bad. Head is secured by a single screw to the stalk so I can swap the cable from the parts mirror if I knew how to disconnect the cable from the mirror itself. The three cables sit into the head, seem to be a spring loaded seat with a ferrule on the end of the cable that then sits into the slots??
Can you push the cables inward to release them from the mirror head and then fish the replacement up through the door, mirror stalk and re-attach? If you release the cables from the mirror head do many tiny springs, clips, and broken plastic pieces come flying out? It seems almost too easy, which is why I'm a bit apprehensive. Searched all over but hard to believe I'm the first guy to try this???

 

I've got a passenger side remote with the same bad cable problem. I'm not sure how to fix it because I don't have it in front of me but I do know you need to remove the mirror from the car door, THEN try to replace the cable. Are the spots where the cable sits slotted? It seems I remember you would push the cable head up and then push the cable through the slot releasing it. Now thinking that was a different non GM car. It has a been a long time since I messed with one and it was a sport mirror on a 73 Camaro but I would think most GM remote mirrors would be similar. Good luck with it.