We access the complete air conditioning system. The pump, condenser, plumbing and the evaporator core. Dash fan operation and radiator temperature.
Air conditioning systems will not work when the refrigerant is low in the system or the electrical portion of system has failed. The manufacturer installs protection devices in the system to protect the system for low refrigerant or high pressure in the system. The refrigerant becomes low due to a leak in the system. Late model vehicles have a separate computer to control the A/C system. Each vehicle has a specific quantity of refrigerant in it. The old fashion way of just arbitrarily adding gas to the system is no longer valid.