- If no sound is coming from the amplifier but the power is on, it could be that the speaker wire coming from the head unit or going out from the amp to the speakers has become damaged. Trace the speaker wiring to and from the amplifier to ensure that it's connected properly, not kinked or bent, and doesn't contain any splices that could ground out the system--possibly damaging the stereo or amplifier in the process.
- If there is no sound coming from the amplifier and it doesn't appear to be turned on, check for a bad ground or power wire. If the amp was wired correctly, the power wire will be red and the ground wire will be black. The ground wire should be securely attached to an unpainted portion of the vehicle's body or chassis. The power wire will likely be traced to the fuse panel, spliced into another hot wire, or connected directly to the battery itself in the engine bay. If either wire is damaged or severed, it's likely that the amplifier will cease to work until the problem is resolved. Ten-gauge wire or bigger should be used for both the power and ground sources.
- Amplifiers generally have a fuse built into the body near the speaker inlets, and this should be checked at the first sign something is wrong. They're usually the two-prong style with the amperage rating written in white on the end of the colored plastic portion. Also, there may be an inline fuse in the red power wire that can blow under power surges. Ensure that all of the fuses are still in good operating order before assuming the fix is something more expensive.
- Some amplifiers require the chassis, or body, of the amp to be grounded in addition to the black ground wire. If you're sure everything is hooked up correctly but the power wire to the amplifier refuses to come on, try grounding the frame of the amplifier to an unpainted portion of the automobile. You can check by baring the ends of a wire and touching one end to the body of the amp, and the other end to a suitable ground on the vehicle. If the amp turns on, drilling and hard-mounting the amp is probably necessary. The screws going through the body of the vehicle and touching the chassis of the amplifier will provide the ground.
