What Causes Intermittent Shaking When the Car Air Conditioner is On?
3 Answers
Here are the specific reasons for intermittent shaking when the car air conditioner is on: 1. Shock absorber system failure: The shock absorber system is mainly responsible for filtering the vibrations generated by the engine during operation. If the shock absorber malfunctions, these vibrations will directly transmit to the steering wheel and the cabin, affecting driving. When the engine is idling, turning on the car's electrical systems can easily cause shaking. The engine increases its load due to the activation of electrical devices, leading to a drop in idle speed. To compensate for the shaking caused by the idle speed drop, the engine automatically increases the RPM. When electrical systems, especially the air conditioner, are turned on, the engine often shakes. This shaking is likely caused by aging shock absorbers and requires timely replacement. 2. Unstable oil pressure: If the engine carbon deposits have been cleaned, the throttle body has been cleaned, and the oil pads have been replaced, but the car still shakes, it is recommended to check the fuel supply pressure and the intake pressure sensor at a repair shop. Abnormal fuel pump supply pressure or incorrect and improper operation of the intake pressure sensor can both cause the car to shake. 3. Cold start: The main reason for car shaking during a cold start is incomplete fuel combustion, resulting in insufficient power. Low ignition energy means that during startup, when the temperature of the fuel and lubricant is low, more fuel is needed to meet the power demand. Over time, the gap in the spark plug electrodes gradually increases, leading to reduced ignition energy and poor fuel atomization, which causes the car to shake. Additionally, aging ignition coils, high-voltage wires of the spark plugs, or electrical leakage can also reduce ignition energy.
After running this auto repair shop for so many years, I've found that nine out of ten cases of AC shaking issues are due to the engine struggling. Think about it - when the AC compressor kicks in, the engine has to handle an extra 3-4 horsepower, which is no joke. If the engine has severe carbon buildup or worn-out spark plugs failing to ignite properly, the RPM drops immediately. Especially at red lights, the car shakes like a sieve. Belt slippage is another common culprit, squealing and making the steering wheel dance. My advice is to first check the ignition system, then perform a compression test, and finally inspect whether the engine mounts are damaged from the vibrations. Don't delay this - the longer you wait, the more expensive the repair gets.
From a mechanical principle perspective, the root cause of AC vibration is essentially a sudden change in engine load. When the compressor's electromagnetic clutch engages, if the engine ECU fails to respond promptly, it results in temporary oxygen deficiency. Based on several cases I've studied: in older vehicles, the issue is often due to carbon buildup causing throttle valve sticking, leading to insufficient air intake; in newer cars, it's commonly caused by clogged low-pressure lines restricting refrigerant flow. Another scenario involves the cooling fan spinning uncontrollably, causing battery voltage to suddenly drop to 11 volts and throwing the vehicle's computer system into chaos. The most troublesome case is a faulty AC pressure sensor - when it provides inaccurate readings, the entire system goes haywire. It's recommended to use an OBD scanner to monitor real-time data streams, with particular focus on RPM fluctuation values and AC pressure curves.
