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What Causes the Abnormal Noise When the Air Conditioning is Turned On in a Mercedes-Benz?

2 Answers

PrestonFitz

07/25/25 5:34am

As a high-speed rotating component, the air conditioning compressor has a relatively high probability of failure, with abnormal noise being a common issue. There are many reasons that can cause abnormal noise in the compressor. For example, damage to the compressor's electromagnetic clutch or severe internal wear in the compressor can both produce abnormal noise. The following are specific reasons: 1. Compressor Electromagnetic Clutch: The compressor frequently operates under high load conditions, transitioning from low to high speeds, placing high demands on the electromagnetic clutch. Additionally, the electromagnetic clutch is usually installed close to the ground and often comes into contact with rainwater and dirt. When the bearings inside the electromagnetic clutch are damaged, abnormal noise occurs. 2. Tension of the Compressor Drive Belt: If the drive belt is too loose, the electromagnetic clutch is prone to slipping; if the drive belt is too tight, the load on the electromagnetic clutch increases. Improper tension of the drive belt can, at best, cause the compressor to stop working and, at worst, lead to compressor damage. When the drive belt is operating, if the compressor pulley and the generator pulley are not in the same plane, it can reduce the lifespan of either the drive belt or the compressor.

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JeffreyFitz

08/10/25 5:48pm

As a veteran mechanic with over a decade of Mercedes-Benz repair experience, I've handled numerous air conditioning noise issues. The most common cause is a loose or aged/deformed AC compressor belt, which produces squeaking sounds upon startup. Worn compressor bearings can also create a metallic humming friction noise, especially noticeable after the vehicle has traveled 70,000-80,000 kilometers. When foreign objects like leaves or paper scraps get stuck in the blower fan blades, they generate rattling noises. Another scenario occurs when there's insufficient refrigerant or air mixed in the AC piping, creating hissing airflow sounds during cooling. I've observed that Mercedes AC pipe brackets are prone to loosening, causing piping collisions that produce knocking sounds over bumps. For these situations, it's best to record the RPM range when the noise occurs and specific sound characteristics - this helps professional technicians diagnose the root cause more efficiently.

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What Causes the Gurgling Sound in a Car's Radiator?

Most of the time, the gurgling sound in a car's radiator is caused by insufficient coolant in the vehicle's radiator. The specific reasons and solutions are as follows: Insufficient Coolant in the Radiator: When there is not enough coolant in the engine, it leads to excessively high temperatures and the presence of air inside, causing the phenomenon of 'boiling over.' This is why you hear a gurgling sound when the car stops. Solution: After venting the air from the engine, add antifreeze. Blown Cylinder Head Gasket: The cylinder head gasket under the cylinder head is blown open by high-temperature and high-pressure mixed gases. If this opening connects to the cooling water passage of the cylinder block, it continuously pumps air into the radiator during the operation of the connecting rod and piston system, producing a noticeable abnormal sound. Solution: Drive the car to a 4S shop for repair or replacement of the cylinder head gasket.

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What are the precautions for manual transmission in Subject 3?

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