Glad you got it working. Sounds like you probably had some corrosion on the terminals and the plugs were making bad contact. If it happens again I would start by cleaning the terminals on the AC amplifier and the connectors.
In the previous 2 ac iterations on the 80, that is correct, because they use a resistor pack with multiple resistors for multiple speeds (low, m1, and m2), but your setup only has 1 resistor (hence only 2 wires). The way i read it, high goes through the relay or transistor, low through the...
That 97 auto a/c system does not have a resistor pack or relay box. By the looks of the diagram, full speed is controlled by a relay and power transistor, and other speeds are controlled by the ac amplifier. Your issue may be the amplifier or the control unit sending the signals to the...