Why does the idle speed increase when the air conditioning is turned on?
1 Answers
Turning on the air conditioning increases the load. The engine load sensor detects the increased load signal and transmits it to the engine control unit (ECU). The ECU then outputs a command to increase the engine speed to handle the additional load. If the idle speed becomes unstable when the air conditioning is on, the following reasons may be the cause: 1. Engine control logic error: The ECU fails to receive the signal indicating the air conditioning is on. When it cannot determine whether the air conditioning is on, the ECU mistakenly interprets it as a temporary high load and attempts to compensate by increasing the idle speed to offset the resistance. When the engine speed drops, it cannot handle the load from the air conditioning compressor, causing the speed to increase again. This back-and-forth adjustment results in unstable idle speed. 2. Air conditioning control circuit error: The circuit fails to send the signal indicating the air conditioning is on. Similar to the first reason, because the ECU cannot determine the air conditioning status, it continuously adjusts the idle speed, leading to instability. 3. Air conditioning circuit malfunction: This causes intermittent operation of the air conditioning. When the air conditioning is off, the compressor belt runs without load, so it does not affect the engine load. However, intermittent operation of the air conditioning compressor forces the engine to continuously adjust the idle speed, resulting in instability.
