78 vette with power windows. The (power) window regulator spring where it mounts on the regulator moves out off it's center shaft a tad bit and the window channel strikes it on the way down (or up) and sometimes stops the windows progress. Had the regulator and channels out last fall and changed rollers and tightened everything up. Put all new weatherstipping on the doors  then and put new t-tops seals on a few weeks ago. Window worked good till I adjusted the glass so it would fit correct. I'm thinking I didn't set the spring tension right( if there is a proper tension) when I put the spring on the shaft and it's too loose. Is there a clip or something that holds that spring on the center shaft? The end of the spring has a nipple on it's shaftthat keeps it in check. Any idea's. Thanks .

The regulator spring should have tension on it all the time. It's that tension that kinda keeps it "in the groove". I replaced the spring in my driver's door years ago...with the glass and regulator still in the door, all connected. I made up some new words for the cuss jar, but I finally got it in.
Sorry to say, I do NOT remember how I finally got the dang thing in right, but I do remember there is still blood and skin stuck to the inside of that door. I have seen tech on how to replace the spring with all the guts out of the door somewhere....I'll look and see if I can locate it....hopefully someone else will have the info.

Thanks for the reply. I can relate to the skin and blood statement. Part of the fun...When the window is full up it's possible to access the spring ( with door panel off). I assume the spring tension is at it's lowest when it is raised. The tension rises on the sping when it lowers to assist the window when it is is raised . Is that correct.? I can move the spring and possibly remove it when at top travel. Should it be that loose. ?