The initial inspection of the air conditioning system is performed after the customer's complaints and concerns have been reviewed. Troubleshooting and inspection starts during the test drive and is completed after the vehicle has been pulled into the technician’s bay. The first thing and start of the diagnostic procedure is to verify the customer's complaint.
If the compressor's clutch is unheard during the initial test drive, make sure it's observed in operation in the service bay. Observing the compressor’s clutch in operation is a sure indication that the compressor’s electrical and control system is functioning. Also notice fan speed operation. A weak or inoperative fan will leave the condenser with little or no air flow, deeply affecting the condenser's ability to cool and condense the incoming refrigerant. Visually inspect all hoses and connections for oil spots. Oil on a hose or connection should be checked with a refrigerant sniffer, this is often an indication of a leak in the system.
No matter how well the air conditioning system operates, if the blend doors are improperly mixing heated air with cooled air, the system will perform poorly. The blend door or temperature door is used to blend the heated air from the heater core with chilled air leaving the evaporator core. The temperature of the outlet tube from the evaporator should be cool to the touch, because this tube is on the low side of the system, after the system's metering device.
With a manual air control, the operator can block any air from passing through the heater core with MAX AC, or block all air from passing through the evaporator with the full heat position. The operator can also achieve any variable setting in between. An automated temperature computer controlled system will blend the air to achieve the desired temperature entered into the control head by the vehicle’s operator.