I'm having the same problem with one of my vacs. Aside from replacing it with a functional one, how do you determine if a vac driver is malfunctioning?
Uh, is a vac driver a vac motor?
If so there are a couple of simple ways. Open the
door on the vac and turn it on with the
door open. See if both/ all motors spin. If you do it with the
door closed the suction form the other motors cause it to spin.
A dangerous way you should not do is hold the motor and stick the leads in an outlet or end of an extension cord. You culd also build a cheap test cord from a cord with a mail plug on one end and alligator clips on the other. Bench test the motor by clipping the ends to the motor leads. - MAKE SURE THE MOTOR IS SECURE TO THE BENCH -and then plugging the male end into the outlet.