A/C Clutch & Blower Speed #4 Quit - '85 Jetta

My Dad's '85 Jetta suddenly lost the highest speed on the blower (#4), and also lost the air conditioning clutch, at the same time. A burning smell came through the interior vents. The blower works fine on speeds 1, 2, and

1. The air conditioning clutch works if you jump a wire from the battery to the clutch. What might be the problem?

Thanks,

- Phil