wdfifteen...Your problem is likely at pin 3. This is a "simplified" diagram which means it is accurate by function/operation...but maybe not exact in other ways.
Both connections marked pin 3 in the diagram are physically in the same place as well as electrically...even though it does not appear so in the simplified drawing. Pin 3 is where the power goes in to the heater control switch and also where it goes out to the Aux Blower Relay. That point is probably disconnected somewhere between pin 4 of the engine compartment controller and pin 3.
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