Engine noise in speakers is a common problem usually caused by improper installation of the radio equipment. When new radio equipment is installed, it is very important that the ground at the head unit and the ground at the amplifier are equal in resistance. If they are not, a ground loop can form which will generate engine noise through the speakers. Eliminating this noise can be a challenge if you do not know where to look.
Instructions
1. Turn on the ohmmeter on and place the red probe on the head unit ground terminal and, at the same time, place the black probe on a metal part of the vehicle body to check the resistance between the head unit ground terminal and the vehicle chassis. Write down the measurement, which should read zero resistance.
2. Repeat step 1, but check the terminals at the amplifier instead. Both readings need to be the same. If they are not, there is excessive resistance on the ground side of one of these two components, which causes the head unit and the amplifier to operate on two different ground voltages This difference causes a small current to flow between the two devices along the ground path. The result is engine noise coming through the speakers.
3. Disconnect the ground wire for the component that has a high ground resistance.Check to make sure the wire is making a good ground connection to the vehicle frame. Clean the point of connection with a file. Reconnect the wire and retest the connection.
Tags: head unit, head unit ground, unit ground, ground terminal, radio equipment