Why does the Prado's water temperature rise when idling with the AC on?

[LaPreston]

Prado's high water temperature when idling with the AC on is a typical cooling system malfunction. This situation is more commonly observed when the vehicle is idling in place with the AC on or when climbing steep slopes with a heavy load, causing the engine temperature to rise, while the engine temperature remains normal when going downhill or driving normally. Causes of cooling system failure: 1. Excessive scale in the engine water passages. 2. Excessive debris on the exterior of the radiator. 3. Deformed radiator fins obstructing airflow. 4. Engine overheating caused by a clogged radiator. Reasons for high water temperature with the AC on: 1. Check if the radiator is leaking. 2. Replace the water temperature sensor. 3. Replace the thermostat. 4. Replace the water pump.