My 1999 C230K has been giving off a "burning" smell. The belts seem extremely tight but look OK. I thought the tensioner was self-adjusting. I had a supercharger seize up on me a few months ago and I don't want something else to happen. How do you check the belt tension? The belts deflect only about 1/4 inch when pressed. Could the tensioner be bad?

Serpentine belts should not be very tight.

usually you can get maybe a half inch of tensioned slack out of that belt.

It should not feel that tight.

Did you have a factory compressor put back on?

Was the pulley the same size as the old one.

Check the numbers on the belt and call the dealership to see if their numbers jive with the belt you have on the car.

Also pull out your owners manual and find the belt routing picture and make sure the belt is routed right.