Any advice before me having to ask for a service call? Dryer won't start. Dryer power is present, interior light goes on, dryer door switch turns off light. No circuit breaker tripped for main power. Dryer is approx 4 yrs old. Start switch button "clicks" when pressed as is normal but does not start on any dry cycle. Unplugged power cord and removed back panel but can see no damaged part. I'm not familiar with internal parts but love to hear any ideas to check! Thanks in advance. --John