My central air system will not turn on. I have sprayed it out and checked the circuit breakers. And am nor replacing the fuses. I how I tell if it needs replacing rather than a recharge.

From the thermostat to the capacitors you must check ALL those electronic components to see which one is causing your problem. An AC tech is advised.

Do you know how to use a VOM? Check for 24VAC at the contactor with the thermostat calling for AC. No 24VAC? problem is before the condenser, thermostat, control board, wiring. 24VAC at the contactor? Bad contactor, compressor, capacitor, wire