Model WED 8300SW0 whirlpool dryer. Heat went on when I turned it on but drum does not spin. No noise when it is manually spun.. When I try to turn it on, the door switch seems to cause a click when it is opened. Belt, all wheels and pulley all work and can easily turn the drum with the belt from the back (which I opened to view the internal parts). No noise when I spin the motor. internet says it may be several things. How do I rule out those which it is probably not given the above