LEFT: With the parts clean, start reassembling. We started by applying lithium grease to the control shafts before installing them.

BELOW LEFT: With the control shafts greased, bolt them to the control unit halves. There is a left and a right on A/C cars; the shaft with the flat side will go on the left half.

BELOW: You will need to calibrate each half to the control face. First, install one of the plastic wheels into one of the halves. Roll the wheel forward until it stops and note the position of the shaft. It should be all the way back, which is the location of the shaft when the control unit is in the off position.