1989 S-10 Blazer. Is there a relay switch for the rear defogger? I have checked all the lines on the rear window and the fuse in the fuse box. Is there any other reasons why the rear defogger isn't working?

I'm in the same boat.

1989 S10 Blazer w/4.3L. Rear defogger doesn't work. I was going to put a multimeter on it tomorrow to see what's going on back there and if the juice is flowing. Perhaps a thin wire separated. If I come across anything that looks like it might help, I'll stick it in here.

check the connector on the window itself may be loose

Aha!

I did a search and came up with this:

Service Bulletins
Technical service bulletin from Chevy re: 1989 Chevy Blazer

TSB# 9152210 NOV 92 Tailgate Window Defogger - Will Not Function

Apparently, this is an issue that has shown up before. I will keep looking and see what I can find.

Roger that maspoon,

Thanks for the heads up. It'll be the first thing I check.