Belt slipping?

Whenever i get out of my truck after a short drive, i always have a burning rubber smell. I have checked to make sure there was nothing on the exhaust and i don't have any brakes sticking, but if I put my truck in neutral and rev to about 3000rpm i can smell burning rubber. I was just wondering if anyone else has had any problems with their tensioner not keeping enough tension on the drive belt allowing it to slip.

 

Push in on the belt in numerous spots. Does it feel snug? What does the belt look like? Cracks in grooves/etc?

 

It doesn't feel as snug as it should be, and when i went to back the tensioner off it did not take much effort, and it has a couple of shallow groove marks in the backside of the belt but the grooves themselves look fine, the belt itself is only about 6 months old, I replaced it along with an idler pulley that went bad this summer

 

I wonder if that's what the burning rubber smell is about? What caused those groove marks on the backside of the belt?

Assuming proper belt orientation. See post #2 in this thread for that:

https://www.tacomaworld.com/threads/lost-bolt-for-idler-pully.412247/#post-11687151

 

I had a similar smell indicate that my ac compressor clutch was failing.