Troubleshooting and Repair of Car Air Conditioner Electromagnetic Clutch Malfunctions

Burnout of the AC electromagnetic clutch coil is mainly caused by excessively high pressure in the AC system (aside from product quality issues). Excessive pressure increases the resistance to compressor operation beyond the electromagnetic attraction force of the coil, causing relative sliding friction between the driving and driven plates of the clutch, which leads to overheating and burnout.

There are three main causes of excessively high pressure in the AC system:

① Running the air conditioner for extended periods while the vehicle is stationary, the engine is idling, and the car is exposed to direct sunlight.

② Using the air conditioner for long durations at high load when the radiator cooling fan is malfunctioning (note: the radiator cooling fan is shared with the AC condenser fan).

③ Overcharging the refrigeration system with freon.

Troubleshooting and Repair Case

When the compressor starts operating, observe the sight glass on the receiver drier: if no bubbles are visible at all, this indicates an anomaly. Connect high and low-pressure gauges to the refrigeration system for pressure testing—you will find that both the high-side and low-side pressures deviate from the standard range. This is a clear sign of overcharged refrigerant.

To resolve the issue, release an appropriate amount of refrigerant from the low-pressure side, adjusting the pressure to the optimal range:

High-side pressure: 1.2–1.8 MPa

Low-side pressure: 0.15–0.30 MPa

After adjustment, the malfunction will be eliminated.

Preventive Measures

To avoid such malfunctions, do not use the air conditioner under the following three conditions:

① If the refrigerant charge exceeds the specified amount, release the excess immediately before using the AC. To check the refrigerant level: observe the sight glass on the receiver drier when the compressor is running. The absence of bubbles means overcharging (release refrigerant appropriately); excessive bubbles indicate insufficient refrigerant (add an appropriate amount).

② Stop using the AC immediately if the radiator cooling fan stops working due to a malfunction. Otherwise, the refrigeration system will generate ultra-high pressure, causing the electromagnetic clutch to slip and burn out.

③ Avoid using the air conditioner when the vehicle is stationary and the engine is idling.