* Increased Engine Load: The AC compressor requires power from the engine. This increases the engine's workload, leading to higher operating temperatures. The engine has to work harder to both power the car and run the AC, generating more heat.
* Reduced Cooling System Efficiency: If the cooling system is already operating at or near its limits (due to low coolant, a clogged radiator, a faulty water pump, a malfunctioning thermostat, or a failing fan), the added heat from the AC compressor can push it over the edge, resulting in overheating. The system simply can't dissipate the extra heat quickly enough.
* Airflow Restriction: A dirty condenser (part of the AC system located in front of the radiator) restricts airflow, hindering the radiator's ability to cool the coolant. This is exacerbated when the AC is running, as the condenser is actively working.
* Fan Issues: The cooling fan is crucial for drawing air across the radiator. If the fan clutch is failing, the fan isn't running at full speed or is malfunctioning, the system can't dissipate enough heat, particularly under the extra load of the AC.
In short, the AC doesn't directly cause the overheat. It highlights an existing problem with the car's cooling system. If your car overheats with the AC on, it's a strong indicator that you need to have your cooling system thoroughly inspected and repaired.
