our Kenworth a/c simply will not work with out the main fan on, just blow hot air or mildly cool. any suggestions

What kind of condition is the condenser in ? Is it clean ? or is it full of corrosion, dirt and bugs ? 8) 8)

You may need to have it charged. It could be low on refrigerant. Being low on antifreeze can also make your a/c blow warmer.

All of what TK & G-da-Man said! Plus...are the heater line valves closed? Makes a difference over 90 degrees.

Big thing is the condition of the condenser and radiator. If they are plugged with dirt, leaves and bugs..then you won't get proper air flow throw them and no A/C, with out the truck moving and the fan engaged...been there...paid for that!! The condensor needs to be pulled off the front, washed and blowen out from the back..you cannot wash or blow the dirt through towards the radiator !! Also..kinked hoses from the condenser to the drier....dirty cab filters..or a bad cab "coil" or bad compressor.

Lot's of things to go wrong with A/C.