Several common wiring errors:

1. After connecting the line, press the horn button, the horn will not sound, and the relay will not clatter, which means that the blue line and the white line are wrongly connected. They should be connected to the power supply of the original car respectively. They can connect the horn line of the original car or the battery.

2. The air pump makes a whine sound but the horn doesn't sound, which means that the positive and negative terminals under the air pump are connected reversely. The yellow wire should be inserted into the positive pole and the black wire into the negative pole.

3. The sound of the horn is not stable, and sometimes it will break. That's because there is paint on the frame where the black wire is grounded, which affects the normal power on of the negative pole. As long as it is connected to a good power on position, it is OK.