A newly installed car stereo system can be plagued with a distant, faint whine that seems to change pitch along with the engine's RPM. Often called Alternator Whine, the sound is not exactly caused by the alternator. In most cases, it is usually caused by a voltage differential created by any number of wiring-related factors, including the number of ground paths and the way the wires are run. Solving this problem involves inspecting each component of the car stereo, from the amplifiers to the head unit itself.
Unplug the RCA cables from the amplifier and insert a muting plug to isolate the noise. Check the components that are upstream of the amplifier if the noise stops. Plug the RCA cables from the head unit directly into the amplifier. If the noise returns, the head unit may need to be replaced.
Check the ground wires for your stereo components. All ground wires for the stereo system should be securely connected to the bare metal of the vehicle's chassis. Use sand paper to remove any surface rust from the grounding area.
Inspect the wire routing for your car stereo system. The RCA wires should run on the opposite side of the power feed. Reroute the RCA wires along the driver side of the vehicle and the power feed along the passenger side of the vehicle to avoid interference between the two.
Install a noise filter onto the power feed between the alternator and the battery. A noise filter helps reduce the amount of noise passed through to the car stereo system, but it does not eliminate the noise. Noise filters can be used as a last resort if nothing else works.
