Why does the engine make abnormal noise when the air conditioner is turned on but not when it is turned off?

[DelLayla]

When the air conditioner is turned on, the engine makes abnormal noise, but when it is turned off, there is no noise. This may be caused by the high-speed operation of the car radiator cooling fan generating noise, wear or lack of lubricating oil in the air conditioner blower motor bearings, or looseness or aging of the air conditioner compressor belt. The specific reasons are as follows: Noise from the car radiator cooling fan: When the car fan receives the command to turn on the air conditioner, it will operate at high speed. Normally, it works when the water temperature is high, but after the air conditioner is turned on, it needs to operate continuously, which significantly increases the noise. When the fan becomes unbalanced due to dirt accumulation, the noise becomes louder, accompanied by body vibration. Wear or lack of lubricating oil in the air conditioner blower motor bearings: When the blower motor bearings are worn or lack lubricating oil, noise will also occur, usually a sharp sound. Another reason is that if the air conditioner filter is not replaced in time and becomes unbalanced due to dust accumulation, it can also cause resonance and abnormal noise. Looseness or aging of the air conditioner compressor belt: When the air conditioner is turned on, the compressor engages, increasing the load on the belt. If the belt is loose or aged, it will produce abnormal noise.

[DelAaliyah]

I've had a similar experience. The most common cause of engine noise when the AC is on is an issue with the AC compressor drive belt. Over time, the belt can age and become loose. When the AC is turned on, the compressor load increases, causing the belt to slip and produce a squeaking sound, which disappears when the AC is off and the load decreases. The compressor itself might also make noise due to sticking or bearing wear. I recommend first checking if the drive belt has cracks or is loose. You can tighten or replace it yourself at a low cost to solve the problem. If it's a compressor issue, professional diagnosis and repair are needed. Don't delay too long to avoid increasing the engine's burden. For regular maintenance, periodically check the belt and the condition of the AC system to reduce the likelihood of noise. Also, pay attention to whether the refrigerant is at the proper level, as too much or too little can affect the system's operational efficiency.

[PeterDella]

As a car owner, I always check the drive belt first when the engine makes abnormal noises with the AC on. A worn-out belt tends to slip, producing sharp squealing sounds, which stop when the AC is turned off due to reduced load. Poor engagement of the compressor clutch can also cause similar issues. I make it a habit to inspect the belt and its bracket every six months—tightening or replacing them if loose, rather than waiting for the noise to worsen. If the sound persists, it might indicate damaged compressor bearings, requiring professional diagnostic tools. Hot weather increases the likelihood of such noises as it adds extra strain on the engine. Remember, minor fixes prevent major troubles; neglecting them could lead to belt failure, compromising driving safety. Regularly replacing refrigerant also helps maintain the system in good condition.

[JordanRose]

Finding abnormal noise when the AC is on that stops when turned off is often due to belt slippage or compressor issues. A loose belt rubbing against the pulley will cause squeaking, while turning off the AC eliminates noise if the compressor is faulty. First, visually inspect the belt's condition—replace it if cracked. Noise type can also indicate the problem: a clunking sound may suggest loose engine mounts. Don't delay repairs to avoid damaging engine components. Simply replacing the belt costs just tens of yuan. The cooling system's condition is also crucial—ensure proper heat dissipation to minimize noise occurrence.

[JosephineLynn]

The engine makes abnormal noises when the air conditioning is on but stops when it's off, usually due to aging drive belts or compressor load issues. Drive belt repairs are inexpensive, and the noise typically disappears after replacement. If it's a compressor malfunction, the repair cost is higher. I'd prioritize trying a belt replacement first for peace of mind and cost savings. Wear on the compressor clutch can also cause similar symptoms, requiring professional diagnosis. For prevention, regularly inspect belts and the AC system, especially before peak summer usage. Ignoring abnormal noises can lead to more severe issues like engine overheating, increasing accident risks.

[StLaura]

The air conditioner is quiet when turned off but noisy when turned on? This is often caused by faults in the air conditioner compressor-related components. A slipping drive belt may cause a squealing sound, while compressor jamming can lead to abnormal noises. Location judgment: If the sound comes from the front, it might be the belt; if from the rear, it could be the compressor. From a safety perspective, immediately stop the car to check if the belt is broken or damaged to avoid affecting engine operation. Regular replacement of the belt and maintenance of the air conditioning system can prevent this. Too much or too little refrigerant can also increase the risk of abnormal noises. While driving, reduce the maximum load on the air conditioner to protect the overall safety of the vehicle.