1> When you are not using our original audio cable, please check if your audio cable is suitable for our camera.
2> Please check if there is any collision between the lines.
3> If the line is connected, there will be no sound when the speaker cable touches the speaker cable. There is also no sound when the power cord touches the speaker cable.
4> If the problem still here,please use a single speaker to connect a group of audio cables to test the car radio. The four speaker cables are connected separately to see if there is any sound.