Lift the hood of the vehicle to access the battery terminals. Remove the rubber coverings that protect the terminals from debris.
Loosen both the positive and negative battery terminal clamps to free the cables connected to each lead post. Use an adjustable wrench if the exact size for your vehicle is unknown.
Remove the negative battery cable from the negative terminal. The negative battery terminal is covered by a black covering and has a "minus" sign on or near the terminal.
Place the ring terminal included in the amplifier wiring kit onto the positive battery lead post. Tighten the positive battery cable clamp to the post, securing the ring terminal to the lead post.
Remove the fuse from the fuse holder on the ring terminal.
Connect the power supply cable (usually a long, blue cable) to the ring terminal.
Use a drill to create an opening in the firewall of the vehicle. The opening will lead into the cabin on the driver's side of the car. Place a rubber grommet in the new opening to protect the power supply cable from being damaged by the sharp edges of the firewall hole.
Feed the power cable into the inner cabin of the vehicle through the firewall.
Remove the vehicle's stereo as described in the repair manual. Disconnect the stereo wiring from the rear panel of the factory stereo. If your car stereo is able to accept amplifier wiring directly, skip to Step 11.
Connect the stereo wiring from the vehicle to a wiring harness adapter. The stereo wiring plugs into the adapter one way only. Plug the wiring harness adapter leads into the corresponding outlets on the rear panel of the stereo.
Plug the patch cables from the amp wiring kit into the wiring harness adapter leads (or directly into the stereo, if possible). Feed the patch cables through the back of the stereo mounting dock of the vehicle. Consult the vehicle's repair manual for options for routing the cables to the rear of the vehicle.
Lift the carpeting on the driver's side of the vehicle to lay the power supply cable to the rear of the vehicle. Replace the carpeting once the wiring has been routed.
Run the patch cables to the rear of the vehicle on the opposite side of the car. Running the cables together will cause interference in the signal.
Plug the patch cables into the outlets on the amplifier. Connect the power supply cable to the input labeled "PWR," or "power in."
Connect the grounding wire from the amp wiring kit to the amplifier. Connect the wire to a bolt or screw in the rear area of the car that is directly connected to the frame of the vehicle. Any bolt will serve as an adequate grounding source as long as it is less than 20 inches away from the amplifier. Return to the battery.
Replace the negative battery cable clamp onto the negative battery terminal. Tighten the cable's clamp to the lead post with the wrench.
Replace the fuse holder into its compartment on the ring terminal and close the vehicle's hood.Car amplifiers are commonly used to upgrade a stereo system's volume and clarity. The amp boosts the signal from the stereo head unit to provide more power and a clearer signal to the vehicle's speakers. The amplifier uses a direct connection from the vehicle's battery for power. To connect the amp to the battery, you must either find an opening in the firewall between the engine and the inside of the vehicle, or create one.