Hi,
The 1988 Schematics indicate the following:
12 LT Blue = Switch terminal C = Power input to speed switch (from climate control switch) & also low speed (to resistor block Terminal #3).
12 LT Green = Switch terminal A = Medium 1 Speed output (to resistor block Terminal #2)
12 Tan = Switch terminal D = Medium 2 Speed output (to resistor block Terminal #1)
12 White/Black = Switch terminal B = High speed output (straight to blower motor)
Also, yours likely melted due to bad/corroded connections. Any replacement (new) connectors should be soldered on (Not just crimped) to be sure you get good connection for this high amperage circuit. :mrgreen:
-Nick :!: