2008 Silverado rear window defroster

[327chevy]

I just recently noticed my rear defrost not working on my '08 Silverado. I checked the fuse and relay to begin with. Fuse was good but relay was corroded on one pin. Cleaned that all up and put dialectic grease on them. I used my volt metre to check for voltage at the grid terminal on the drivers side and I'm not getting any. So where is the best place to look for a bad wire connector or broken wire?