What Causes Car Body Vibration When the Air Conditioning is On?
2 Answers
Car body vibration when the air conditioning is on is caused by carbon deposits on the spark plugs and engine intake valves. The functions of car air conditioning include: 1. Achieving a cooling effect through the continuous transformation and circulation of refrigerant; 2. Using the engine coolant, waste heat, or heat generated by a burner as a heat source for heating. The heater then warms the air, which is blown into the car by a blower, raising the temperature at the air outlets for heating purposes; 3. Drawing in fresh external air for ventilation and air exchange, which also helps prevent windshield fogging; 4. Removing dust, odors, smoke, and toxic gases from the car's interior to freshen the air, as well as humidifying the air to increase its relative humidity.
I remember my old car had a similar issue where the whole body would shake when the AC was turned on. This is usually because the AC compressor increases the engine load, causing unstable engine RPM. Possible causes include worn spark plugs or aging ignition coils leading to incomplete combustion; loose or worn AC belts reducing transmission efficiency; loose engine mounts degrading vibration damping; a dirty throttle body with carbon buildup affecting idle control; and sometimes insufficient or old engine oil exacerbating the shaking. For troubleshooting, you can first check if the belts have cracks or are loose, and see if the spark plugs need replacement. If the car idles smoothly but shakes when the AC is turned on, it's likely a compressor load issue. Ignoring it long-term can lead to faster engine wear or even stalling, which isn't worth the risk. I recommend taking the car to a repair shop for a full inspection over the weekend—don’t delay like I did, as it ended up costing me a lot more for new parts.
