If you hear a whine or low hum through your car stereo or audio system, it may be coming from your engine. There are two problems that can cause engine noises through an audio system: ground loops and electromagnetic interferences. On the former, it is a wire not correctly connected to the device's ground or the power source's ground. On the latter, there is too much current for the audio wire to handle. If you eliminate these engine noises yourself, you can save money while brushing up on your automotive repair skills.
Follow the amplifier's ground wire to where it is secured to the vehicle's frame. There will be a small ring connecting the wire to the frame. Make sure the ring is completely tightened, and there are no gaps. Tighten the ring with pliers, if needed.
Find a solid place on the vehicle's frame, away from the ring, to secure the ground wire.and scrape away any paint, rust, or rubber. While wearing gloves, use a large razor blade or another scraping device to scrape away the excess debris. Make sure the metal is completely visible before securing the wire.
Secure the amplifier's ground wire to the clean area using tape. This is a temporary measure.
Bolt the wire to the frame so it is tight and secure. This will help to secure the connection of the ground wires and eliminate ground loops and electromagnetic interference.
Check and make sure all the wires are still connected, then test the stereo.
