Since the other command functions work, the top suspect is the chuff switch. However, I'd clean up the wireless tether wiring to make sure you don't cook some other components.
The chuff switch is located above the rear driver on the rear set of drivers. The picture below shows the location of the cam that actuates the chuff switch. The actual chuff switch looks like the other shot, though the colors of these vary with models, years, and the phase of the moon.
Many times you'll find either a wire broken off or the switch lever just needs a little bend to get it back in operation. If you need a new switch, they're cheap and readily available as well.
