5 common faults of AC charging gun for new energy vehicles

2. Failure of locking mechanism

Performance: When the EV charging gun cannot be properly locked into the vehicle's charging port, the meter displays "abnormal charging connection" or the charging indicator does not light up.

Causes:

a. Mechanical jamming of the locking mechanism or internal switching circuit failure.

b. Abnormal feedback signal voltage (e.g. the feedback voltage is always low, causing the system to misjudge the locking).

3. Signal line failure (CC/CP line)

Performance: The vehicle cannot recognize the charging gun connection, and the instrument does not indicate charging.

Causes:

a. CC (Charging Connection Confirmation) or CP (Control Pilot) line is disconnected or has abnormal resistance.

b. Charging gun internal CC terminal resistance value is abnormal (1.5kΩ when normal unlocked, 3.3kΩ after locking).

4. Poor Grounding or Short Circuit Fault

Manifestation: power limitation while charging, meter prompts poor grounding of charging socket.

Causes:

a. Charging gun or socket grounding wire is not properly connected, or metal parts are not grounded (e.g., part of the charging pile card swipe part is not grounded).

b. The internal insulation of the charging gun fails, resulting in a short circuit between the phase wire and the grounding wire.

5. Temperature or communication abnormality

Manifestation: sudden jumping of the gun during charging, or charging stops before the battery SOC is full.

Causes:

a.Battery temperature is too high triggering thermal protection, or the charging pile detects overcurrent/leakage risk.

b. Vehicle BMS (battery management system) and charging pile communication module failure.

Detection methods and maintenance process

1. Visual inspection and basic testing steps:

1.1 Check whether the charging gun plug terminal is ablated, whether the wiring harness is broken, and test the jack tightness.

1.2 Measure the resistance value of the CC terminal and PE ground terminal of the charging gun (1.5kΩ and 3.3kΩ respectively before and after normal locking).

1.3 Use a multimeter to detect the voltage of CP terminal (normal is about 12V).

2. Insulation resistance test procedure:

2.1 Use an insulation tester to measure the insulation resistance between L1, N wire and PE wire (normal should be more than 220MΩ).

2.2 If short-circuit is found, it is necessary to investigate the wiring harness breakage or internal component failure.

3. Locking mechanism function test procedure:

3.1 Read the locking signal voltage through the diagnostic instrument (the feedback voltage should be 11V when locking, and 4V when not locking).

3.2 Manually test whether the locking pin is flexible, to exclude mechanical stalling.

4. Communication and system diagnosis Procedure:

4.1 Use a fault detector to read the fault codes of OBC (on-board charger) and BMS (e.g. "P142C16 OBC input low voltage", etc.).

4.2 Check the CAN bus communication voltage (e.g. CAN-H is 2.5-3.5V, CAN-L is 1.5-2.5V).

5. Environment and load test procedure:

5.1 Simulate shaking the charging gun and observe whether it triggers tripping (to troubleshoot poor contact).

5.2 Test the charging current under high temperature environment to determine whether the gun is tripped due to temperature protection.

Prevention and maintenance recommendations

1. Select qualified charging equipment: avoid using "ground-free" charging guns, and give priority to brand-name original products.

2. Regularly check the wiring harness and plugs: especially for the frequently used slow charging guns, pay attention to the terminal wear and insulation aging.

3. Avoid charging in harsh environments: Humid and high temperature environments are prone to short-circuiting or corrosion, so it is recommended to use indoor charging posts.