What Causes Severe Vibration When Turning on the Air Conditioning in a Car?
3 Answers
The following are specific reasons for car vibration when the air conditioning is turned on: 1. Shock absorber system failure: The shock absorber system is primarily responsible for filtering engine vibrations during operation. If the shock absorbers malfunction, these vibrations will directly transmit to the steering wheel and cabin, affecting driving. When the engine is idling, turning on electrical systems inside the car can easily cause vibrations. The increased load from electrical devices causes the idle speed to drop, and to compensate for the resulting vibration, the engine automatically raises the RPM. Turning on electrical systems, especially the air conditioning, often leads to engine vibration. This vibration is likely due to aging shock absorbers and requires timely replacement. 2. Unstable oil pressure: If the engine carbon deposits have been cleaned, the throttle body washed, and the oil pads replaced, but body vibration persists, it is recommended to check the fuel supply pressure and intake pressure sensor at a repair shop. Abnormal fuel pump pressure or incorrect intake pressure sensor readings can both cause body vibration. 3. Cold start: The main reason for body vibration during a cold start is incomplete fuel combustion, resulting in insufficient power. Low ignition energy means that during startup, when fuel and lubricant temperatures are low, more throttle is needed to meet power demands. Over time, the electrode gap in spark plugs gradually widens, reducing ignition energy and impairing fuel atomization, leading to body vibration. Additionally, aging ignition coils, high-voltage wires in spark plugs, or electrical leakage can also decrease ignition energy.
When I turn on the AC while driving, the car shakes noticeably, mainly because the engine load suddenly increases. The AC compressor draws too much power when it starts up. If the engine itself has carbon deposits, worn spark plugs, or faulty ignition coils, the shaking becomes more pronounced. Last time I encountered this issue, cleaning the throttle body and fuel injectors improved the situation. Another possible cause is damaged engine mounts, which lose their damping effect, allowing vibrations to transfer into the cabin. Regular maintenance can prevent such issues—for example, checking spark plugs every two years. If the shaking is accompanied by unusual noises, you should stop and inspect the vehicle immediately—don’t overlook driving safety due to minor problems. By the way, turning on the AC during a cold start is more likely to cause shaking, so it’s recommended to warm up the engine for a few minutes before using the AC.
As an enthusiast who often tinkers with car repairs, I believe that severe shaking when the AC is on is a result of excessive engine load. When the compressor is working, the engine requires additional power. If the voltage is unstable or the alternator is aging, and the battery can't keep up, the shaking becomes more frequent. I've personally checked the ignition system—faulty spark plugs or coils causing poor ignition make the car gasp for breath; loose belts or a stuck compressor also increase resistance. A simple DIY is to use a multimeter to check if the voltage is normal; if it's low, try replacing the battery. Also, a clogged idle control valve can cause unstable RPMs, and cleaning it can help. It's good practice to warm up the car before using the AC to reduce sudden load.
