Frigidaire dryer isn't working

[streetdoc]

I own a Frigidaire stack washer/dryer. They were included in the purchase of my home about 4 months ago. Both have worked perfectly. I put a load of clothes in the dryer and turned the start knob. Nothing. Well, next to nothing. When I hold the knob in the "start" position I can hear the timer working. The washer works fine still. The door switch has the same resistance as usual. I removed the front and rear panels and blew out what dust and lint there was with a compressed air cannister. The drum rotates relatively easily. The belt seems ok. That is the limit of my troubleshooting ability. Any ideas as to what the problem might be? Thanks very much in advance.