The original ad heater motors have two wire coming out of the motor.One wire is grounded to the unit like the picture dads50 provided.I would put the reducer after the switch close to the heater.Make sure you put that voltage reducer in a place where nothing will touch it.The reducer will get extremely hot and can cause a fire.Mount it to a metal surface,it will act as a heat sink.I would even put a inline fuse in the system.

Tim


1951 3100 Chevrolet
1951 Chevrolet Suburban Carryall
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