Why does the noise persist after replacing the new belt when the air conditioning is turned on?

[EmersynLee]

Replacing the new belt but still hearing noise when the air conditioning is on is due to insufficient belt tension or excessively high refrigerant high-pressure, or issues with the compressor's clutch. Choosing the appropriate air conditioning temperature: In summer, many people prefer to set the temperature very low. However, setting the temperature too low can affect health, so it's essential to adjust the air conditioning temperature appropriately. The most comfortable temperature for the human body is between 20°C and 25°C. Above 28°C, people feel stuffy, and below 14°C, they feel cold. Therefore, the air conditioning should maintain the car's interior temperature between 18°C and 25°C. Setting the temperature too low can easily make people sick. Do not immediately activate the internal circulation upon entering the car: When the car has been parked under the scorching sun for a long time, some car owners tend to turn on the air conditioning and activate the internal circulation immediately after starting the car, thinking it will cool down the interior faster. However, since the interior temperature is higher than the outside temperature, this approach is ineffective. Upon entering the car, it's better to first open the windows for ventilation and turn on the external circulation to expel the hot air. After the interior temperature has dropped, then switch to internal circulation.

[SanRowan]

As a seasoned driver with years of experience, I think it's quite common for the belt to still make noise after replacement when the AC is on, possibly due to insufficient belt tension during installation. A loose belt tends to slip and produce squeaking sounds, especially when the AC starts and the load increases. Additionally, worn compressor bearings can also be an issue, as turning on the AC increases the load and makes the noise louder. I've encountered this situation in my own car—after replacing the belt, I didn’t pay attention to the tension, but it became quiet after adjusting it tighter at the repair shop. Another possible cause is an aging tensioner pulley, which is responsible for keeping the belt tight and can wear out over time. I recommend manually checking the belt first: after parking, press down on it—if it can be pressed down more than half a centimeter, it’s too loose and needs adjustment. If that doesn’t solve the problem, the compressor or tensioner pulley might be faulty and need replacement. For safety, don’t delay—address the issue early to avoid a breakdown on the road.

[Alivia]

I enjoy doing my own car maintenance. After replacing the new belt, if it still makes noise when the AC is on, we need to troubleshoot step by step. The most common causes are improper belt tension adjustment or a faulty tensioner pulley. That small tensioner pulley component is responsible for keeping the belt tight - if its bearing fails, it will slip. The AC compressor itself could also be malfunctioning; worn rotating parts can generate noise, especially noticeable under high load. Additionally, if the belt wasn't properly aligned during installation, it may rub against edges and produce abnormal sounds when running. My suggestion: start the engine, turn on the AC, and listen closely to locate the noise source. If it's coming from the compressor area, the compressor might be the issue; if there's a general buzzing sound from the belt section, tension or tensioner pulley adjustment may be needed. For DIY solutions, you can use a tension gauge or test tightness by experience, addressing it promptly to prevent further damage. When uncertain, it's more reliable to have a professional shop inspect it.

[VanFelicity]

A friend's car had this issue before, and I strongly advise addressing it immediately as neglecting it poses safety risks. If the noise persists after replacing the belt when the AC is on, it indicates the problem isn't belt-related. The root cause could be a faulty compressor bearing or tensioner pulley failure. The noise becomes more pronounced under high compressor load, and prolonged neglect may lead to belt snapping or system damage, compromising driving safety. Alternatively, it might be misdiagnosed fan or other component noises amplified by increased cooling system pressure when the AC is engaged. For safety, avoid driving with the AC on—pull over to inspect or head straight to a repair shop for thorough troubleshooting. Never underestimate abnormal noises—they often signal underlying major issues.

[KendraRose]

From a cost-saving perspective, if the belt has been replaced but the noise persists when the AC is on, it's often due to minor unresolved issues. For example, improper belt tension causing slippage can be fixed with a simple adjustment, or a loose tensioner can be replaced at minimal cost. However, compressor bearing issues require caution—once damaged, they produce loud noise and incur high repair costs, especially when the AC increases the load. You can perform a preliminary self-check: after the engine cools, press the belt to see if it feels loose; turn on the AC and listen for changes in noise—if the noise is concentrated near the compressor, it indicates a major fault. Additionally, aging fan systems can lead to misdiagnosis, so don’t waste money on a new belt unnecessarily. It’s advisable to address these issues early to prevent minor problems from escalating into costly repairs.

[VonTalia]

Last year, my car also had a new belt replaced, but it still squealed when the AC was on, which was quite a hassle. Later, I found out the belt tension wasn’t adjusted tightly enough, causing it to slip under the increased load from the AC. After having a mechanic tighten it at the repair shop, the issue improved significantly. However, the tensioner pulley then revealed its problem—the bearing was worn out and making noise. The compressor shouldn’t be overlooked either, as a faulty bearing can cause louder noises when the AC cycles on and off. In fact, many unusual noises come from the tensioner pulley or compressor rather than the belt itself. Here’s a tip: when replacing the belt, always inspect the entire system, not just one part. Early checks can save a lot of trouble.