OK.. I got a call from my mother that her AC isn't cooling off the house. I have no errors on the furnace. The furnace appears to be wired properly, as well as the thermostat. What I am seeing, and what the diagrams read, When the furnace is heating the house, the relay sends the current to the blue wire, Medium/Low fan speed, and when Cooling, to the black wire for high speed. The furnace fan is only spinning one speed.. and I am assuming it's medium/low...
From the diagram... I don't understand how the speed control of the fan happens. The SPDT relay sends the voltage to the blue wire, hence medium/low speed... and when cooling, the voltage is sent to the black wire, hence High speed.
My question:
Is the speed control in the motor? Blue wire medium/low and Black wire High... or is it in the relay... partial voltage to the blue wire, then the relay adds voltage to the black wire, sending voltage to both the black and blue wires for high speed?

When I took off the inspection cover, the copper coils on the ends had condensation, but nothing on the fins at all... Maybe it needs a shot of freon... guess I will have her call for a check-up.
Thanks!