Frigidaire dryer isn't working

[streetdoc]

I have a Frigidaire stack washer/dryer. They were included in the price of the home I bought 4 months ago so I’m not sure as to their exact age. They’ve both worked flawlessly. I put a load of clothes in the dryer, turned the switch knob…and nothing happened. The washer is working fine. When I hold the switch knob in the "start" position, I can hear the timer. The door sitch appears to function normally. I’ve removed the front and rear panels. The drum rotates easily. The belt appears fine. There was a considerable amount of dust and lint which I blew out with compressed air. This is the limit of my troubleshooting abilities. Any idea as to what the problem might be? Thanks very much in advance.