What are the methods for diagnosing car air conditioning faults?

[MacBentley]

When analyzing air conditioning system faults, they can be inspected and checked in two main parts: the circulation system components and the electrical control system. Fault inspection and troubleshooting of electrical controls. When the vehicle's air conditioning is not cooling, the control system should be checked. If the control system is intact, then inspect the air conditioning circuit. Diagnosis of cooling system faults is generally conducted using a combination of sensory and instrumental methods. Sensory diagnosis. Use your eyes to observe the entire air conditioning system. First, check the flow condition of the refrigerant in the dryer filter sight glass. Second, inspect whether the connections between components and pipelines in the system are reliably sealed and if there are any minor leaks. Finally, check if the condenser is blocked by debris and whether the cooling fins are bent or deformed. Use your ears to listen for any abnormal sounds from the running air conditioning system. First, listen for any harsh noises from the compressor clutch. Second, listen for any liquid hammering sounds during compressor operation. In the absence of a thermometer, you can touch the surfaces of various components and connecting pipelines of the air conditioning system with your hands. The high-pressure circuit should feel relatively hot, while the low-pressure circuit should feel warm. Instrument diagnosis. Leak detection with a leak detector. Use a leak detector to check for leaks at all connection points in the system. Pressure gauge inspection. Connect the high and low-pressure gauges of the manifold pressure gauge to the system's charging valves, and perform the inspection when the air temperature is between 30°C and 35°C and the engine speed is 2000 rpm.

[BrooklynLynn]

With over a decade of car repair experience, I'll teach you how to self-diagnose AC issues. First, open the engine compartment and check if the compressor belt is loose. Then start the vehicle and turn on the AC to listen for any squeaking noises. When cooling is insufficient, focus on three key areas: whether the condenser surface is blocked by leaves or debris, how long since the filter was replaced, and whether the refrigerant pressure is adequate. Many modern vehicles have fault code functionality - plug in an OBD scanner to check for AC system error codes. If hot air blows from the vents, there's an 80% chance it's refrigerant leakage. The fastest solution is to visit a repair shop and have a technician use fluorescent dye to locate the leak.

[DiRebecca]

Last time I changed the cabin air filter myself, I found that the most common cause of AC odor is moldy filters. But if you smell a pungent sweet odor, it's dangerous—that means coolant is leaking into the evaporator. Don't rush to recharge the refrigerant if you notice poor cooling performance—I learned this the hard way! First, check the AC lines: if the low-pressure line is ice-cold, it's normal; if it's at room temperature, there's definitely a refrigerant shortage. If frost forms, the sensor is likely faulty. Be especially careful with cars that have aftermarket infotainment screens—I once encountered a situation where a loose wiring connection prevented the compressor from starting.

[VonCorey]

Diagnose faults by temperature: An air vent temperature below 7°C is normal. If the dashboard shows an outdoor temperature differing by over 10°C from your phone's weather app, the ambient temperature sensor might be faulty. Hissing sounds during cooling? Beware – it's often a precursor to compressor failure. Musty smell when first turning on AC? Don't panic – running the fan at maximum for three minutes usually solves it. Noticing reduced cooling in prolonged traffic jams? That's insufficient condenser heat dissipation – try turning off recirculation to improve airflow.