Cold water is an effective tool for diagnosing air conditioners suffering from poor air flow, experts said. An air conditioner cools by removing heat. The condenser, which is located in front of the radiator, must dissipate this heat to the ambient air. Normal air flow entering the vehicle's grille-often called ram air-removes much of the heat from the condenser.
Besides ram air, electric or belt-driven fans maintain adequate air flow through the condenser, especially during stop-and-go driving and other high-heat-load conditions.
Inadequate air flow through the condenser results from fan-related problems or from debris (leaves, mud, insects, paper etc.) that clog the condenser fins.
Common signs of poor air flow include inadequate cooling as well as abnormally high pressure on both sides of the refrigeration circuit.
The quickest way to confirm such a diagnosis is spraying cold water into the condenser. If this promptly lowers system pressures, check fan performance and inspect the condenser fins for debris. Note: An overheated cooling system can overheat a condenser.