Heater blower

Anyone have a hint here? (65 A body Dart)
The heater blower works fine at all speeds when A/C or Max A/C is selected but does not work in Heat or Def positions. There is power to the vacuum switch at C1 and C1A as indicated in the diagram. No power to C4A. I replaced the A/C and heater vacuum switch but still the same. I can't locate the blower motor resistor or the resistor bypass switch to check connections. Dart manual not much help.