What is the reason why the Volkswagen's engine speed does not drop below 1500 rpm when the AC is turned on or off?
2 Answers
The reasons why the Volkswagen's engine speed does not drop below 1500 rpm when the AC is turned on or off are: 1. The engine control unit does not receive the signal to turn off the AC; 2. Short circuit in the AC control unit or communication lines; 3. Fault in the AC switch circuit or AC module. The solutions to fix the issue are: 1. Inspect and repair the engine control unit; 2. Reconnect the AC control unit and communication lines; 3. Secure the connections of the AC switch circuit and AC module. The functions of the AC are: 1. To cool, heat, ventilate, and purify the air inside the car; 2. To provide a comfortable environment for passengers, reduce driver fatigue, and improve driving safety.
I had a similar issue with my Volkswagen Passat where the RPM would stay stuck at 1500 when the AC was turned on and wouldn't drop. It happened during summer when high temperatures should cause the RPM to fluctuate and stabilize around 700 with the AC on, but it remained at 1500 RPM, making it noisy and fuel-consuming. I consulted a friend who suggested it might be an idle control system problem, such as a stuck throttle valve or delayed ECU adjustment, causing the engine to constantly strain under the heavy load from the AC compressor. Later, a diagnosis at the dealership revealed a faulty AC pressure sensor sending incorrect signals. Replacing it fixed the issue. If you're experiencing this, don't delay—check the sensor and refrigerant levels first. Otherwise, prolonged high RPM can affect engine longevity and increase fuel consumption. Regular throttle valve cleaning can help prevent such failures.
