I have a Carrier Model 58G5100-2 Series 201 gas furnace. It appears to have a squealing motor in the air handler caused by a loose belt. I'm ready to apply the belt dressing and replace it as needed. Simple question: Where is it and how do I access it? Can't get to it by removing the main access panel and am at a loss. Also have a central air conditioner that also uses the blower. Cannot locate a Users Manual for this old unit.

Thanks for any help available, including tips on how to fix when I find the blower motor belt.