I missed the OP, and it's now ancient history, but just as a general observation, I have not found air poppers to be the most reliable coffee roasters ever designed. Not surprising, they're cheap household appliances designed to operate for a shorter and I believe cooler application. Some have worked a pretty long time, but you never know.
They usually have some kind of thermal cut-off so they don't burn the house down, and that may fail (or work, depending on your perspective) in coffee roasting service. That's easy enough to fix. It might be a metal strip or something in the circuit that you need to crimp shut, or a component that you'll disconnect (with early Popcorn Pumpers it's a rewire job like that, if I remember right.)
I've also had the element coils fail, and I have not had much luck fixing that. Likewise fan motors.
Anyway, the ones I've had were fairly simple devices, no harm in unscrewing them and looking around in there.