Noise from the Air Conditioner Expansion Valve.

Edit： Click：12 Date：2025-09-19

Symptom: When the air conditioner is turned on for cooling, an abnormal humming noise is heard near the firewall.

When the air conditioner is turned off for cooling, the noise disappears.

The humming noise can also be heard from the instrument panel inside the vehicle.

Fault Analysis:

1. Most customer complaints are occasional, and there are three main fault conditions:

01) Some vehicles experience the abnormal noise as soon as the air conditioner is turned on;

02) Some vehicles require the air conditioner to run for a while before the noise is heard;

03) Some vehicles require hot weather for the problem to become more pronounced.

2. Troubleshooting Tips and Response Strategies 1. If a customer complains of a similar abnormal noise,

have the vehicle return to our dealership to confirm the noise and compare it with other vehicles to determine if the noise is abnormal.

2. Check the vehicle's maintenance records. If no relevant repair history exists,

inspect the air conditioner circuit, compressor, blower, air outlet,

and air conditioning unit. If the noise is confirmed to be coming from the air conditioner expansion valve,

follow the corresponding response strategy.

Final cause identified: While the vehicle interior temperature was high,

the air conditioner was turned on for cooling, causing unusual noises at the expansion valve.

Initially, it was suspected that changes in the refrigerant flow caused the expansion valve to vibrate and make unusual noises.

After replacing the expansion valve, the unusual noises disappeared.

Remedy: After replacing the expansion valve, set the air conditioner to 18°C and maximum air volume for 3-5 minutes to

confirm that there were no unusual noises.

Then, adjust the air conditioner to 18°C and level 2 for 3-5 minutes to confirm that there were no unusual noises.

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