I have a Magic Chef - model MCO160UB. when i hit the start button, it does not sound like the fan is running. so the unit will only run about 2 minutes, then shuts completely down. after a few minutes everything is back on - display is lit, light on the inside, etc. also, when i use the fan button, the low speed does not work - only the high speed works. is there a blown fuse or something? this unit is about 1 1/2 years old. thanks!