Why does the idle speed decrease instead of increasing when the air conditioner is turned on?

[OEli]

The reasons why the idle speed decreases instead of increasing when the air conditioner is turned on are as follows: The engine control logic is faulty and cannot receive the signal of the air conditioner being turned on: When it cannot determine whether the air conditioner is turned on, the engine control unit (ECU) mistakenly assumes it is a temporary high load and attempts to offset the resistance at idle by increasing the speed. When the engine speed drops, it cannot bear the load of the air conditioner compressor and increases the speed again. This back-and-forth results in unstable idle speed. The air conditioner control circuit is faulty and cannot send the signal of the air conditioner being turned on: Similar to the first reason, because it cannot determine the status of the air conditioner, the ECU continuously adjusts the idle speed, resulting in unstable idle speed. A fault in the air conditioner circuit causes the air conditioner to work intermittently: When the air conditioner is not working, the air conditioner compressor belt is idling without load, so it does not affect the engine load. The intermittent operation of the air conditioner compressor causes the engine to continuously adjust the idle speed, resulting in unstable idle speed.