Step-by-step Instructions for Wiring an Amplifier in Your Car
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Step-by-step Instructions for Wiring an Amplifier in Your Car

Step-by-step Instructions for Wiring an Amplifier in Your Car

How to connect amp to radio

where should i mount my amp?

Use these guidelines to choose a location to mount your amplifier. a smart mounting location will help your installation go smoothly:

  • Follow the manufacturer’s recommendations for mounting the amplifier and make sure it is secure. an unsecured amplifier could come loose in an accident and injure someone while flying through the vehicle.
  • The amplifier should be at least three feet from the stereo to avoid noise radiated from the car’s electrical system. vehicle . The amp can also interfere with the stereo’s AM/FM reception.
  • Don’t bolt your amp directly to your car’s metal chassis, that leads to noise issues such as buzzing or buzzing ground loops. you can use rubber grommets around the mounting screws to isolate the case. or you can mount the amp on a wooden board or plastic panel and attach it to the car body.
  • An amp produces harmful heat during operation, which its heat sink absorbs and radiates away from the circuit. the amp needs a few inches of air space around it to stay as cool as possible. never mount an amp upside down as dissipated heat will radiate back into the amp.
  • make sure there is enough space to run wiring and adjust controls (gain, crossover, bass boost, etc. .) .

good locations to install an amplifier include:

  • on the firewall (passenger side) advantages: you can use short cables and pigtails. you won’t have to remove a seat or climb into the trunk. Cons: Only very small amps fit here. this puts your amp close to some common noise sources.
  • in the trunk or hatch area advantages: plenty of room for large amps. near the rear speakers. Easy access to amp controls. Cons: You sacrifice some cargo space. longer cables and patch cords are required.
  • under a seat advantages: closer to the receiver, so you can use shorter patch cords and signal cables, which are less prone to noise and signal degradation. closer to the front speakers so that it is easier to route the cable to them. no cargo space is sacrificed. Cons: May have to remove seat to install. warning: removing your seat could disable your vehicle’s srs (air bag) system. only small amps fit. the amp should be protected from rainwater or snow getting into your shoes.

where do I run the cables of my amplifier?

All system wiring should be concealed for safety and to give your installation a nice, finished look. cables must be secured so that they do not interfere with the safe operation of the vehicle. Depending on the location you choose for your amplifier, the wiring may need to be routed under the dash, door skid plate, pillar trim panel, or bottom panel.

The instructions below generally address which panels should be removed and how they are typically removed. panels can often lift at the edges. you’ll probably also need to remove some retaining screws and clips. To avoid damage, always use care when removing panels; a panel tool is useful.

remove the door skid plate

plates are usually removed by lifting the edges to release the clips. some vehicles will have bolts that need to be removed.

remove seat belt

A seat belt may be located in a panel that must be removed. most seat belt anchor covers come off. the seat belt anchor is secured with a large nut or bolt.

remove trim panel from pillar

Remove seat belt if present. remove the screw caps, screws, and plastic retaining clips, if any. lift the edges of the panel to remove it.

remove protection panel

find the screws and retaining clips to remove. pry the edges of the panel to release it and remove it.

cable routing behind dash

When routing the cable behind or under the dash, always secure it with zip ties. make sure the cable does not interfere with any moving parts to ensure safe vehicle operation.

how to install the amplifier

Once the background is covered, it’s time to get to work. gather your gear and tools, maybe a friend and a soda, and give yourself plenty of time.

step 1: disconnect the battery

apply the parking brake and disconnect the negative terminal of the battery to avoid short circuits or electric shock.

step 2: mount the amplifier

mount your amplifier in the location of your choice.

Step 3 – Install the power cord

The power cable from your amp’s wiring kit (typically 16-20 feet long) should run from the battery, through your car’s firewall, through the car’s body to the amp. look for an unused grommet on the firewall or one that already has wires or cables running through it and has enough room for the power cord to run through as well.

If you can’t find an existing grommet, you’ll need to drill a hole through the firewall. make sure you don’t puncture any electrical or gas lines; check both sides of the firewall. use a grommet to protect the wire from fraying and shorting as it passes through the hole.

step 4 – install the fuse holder

The power cable from your amp’s wiring kit may have a fuse holder installed. if so, go to step 5. if not, find a good place near the battery to put the fuse holder (included in the kit); Within 6″ of the battery is best. Be careful: even after a fuse blows, the short length of wire between the battery and the fuse holder will still be live and a potential fire hazard in the event of an accident. fix the fuse holder in a suitable place with a screw or cable tie, so that it does not hang loose or bounce.

Cut a short piece off the end of the power cable (to cover the distance from the battery to the fuse holder location), and strip the insulation from both ends with a wire stripper. Crimp the ring terminal (included in the kit) on one end of the short cable and put the fuse holder on the other end. Strip the insulation from the end of the power cable going to the passenger compartment and connect it to the other end of the fuse holder.

multi-amplifier installations

When powering multiple amps, connect a single heavy gauge power cable from the battery to a distribution block and then connect a lighter gauge cable from the block to each amp. this arrangement minimizes potential noise problems and keeps your installation spotless. make sure the main power cord is thick enough to support the full current draw of all amplifiers.

Refer to our amp wiring diagram to see how the wiring is connected on a typical 2 amp system.

step 5: connect the power cable

Connect the power cable to the positive terminal of the battery (not directly to the battery post). for top mounted battery posts, the most common way to do this is to crimp a ring terminal onto the end of the power cable (many cables in wiring kits come with it already attached). remove the nut from the battery terminal, slide the power cable ring over the bolt that secures the battery terminal to the battery post, and replace the nut. For GM vehicles with a side mount post, we offer terminal adapters that work great.

A wire loom provides additional protection for your cable from the high heat inside the engine compartment. If your kit includes a wire loom, feed it through the power cable until it reaches the firewall and cut it to size. pass another piece over the short power cable that runs from the fuse holder to the battery.

step 6: ground wire: the most important connection of all

As close as possible to the amplifier location, find a stud in the metal frame of your vehicle to use as a ground. If you can’t find a suitable grounding screw or bolt, drill a hole for one; be careful not to puncture any wiring, the gas tank, or a gas or brake line. crimp a ring terminal (usually included with the amp kit) to the short piece of ground wire (also in the kit).

Ground wireScrape away any paint and clean the bolt location thoroughly, and then bolt the terminal tightly to the vehicle’s metal chassis so the ground connection will be bare metal to bare metal. Use a lock washer, a star washer, extra screws, and any other technique or device that’ll keep this connection tight, clean, and electrically conducting. Many people even coat the final connection with silicone caulk to prevent corrosion.

Improper or loose grounding is the leading cause of amplifier problems.

Step 7 – Connect the remote turn-on cable

The ignition cable (also called the remote cable) is located behind the stereo. on aftermarket stereos, it’s usually a blue and white wire. the remote wire will “tell” your amp to turn on every time the stereo is turned on (usually every time the vehicle is started). you will have to remove the stereo to get to this wire. For step-by-step instructions on how to remove your vehicle’s radio, refer to your vehicle-specific Crutchfield™ Master Sheet or read our car stereo installation guide.

Strip the insulation off a small section of this wire from the radio and ignition wire that came with your wiring kit and connect them using solder, a crimp connector, or a positive connector.

ignition signal is +12 volts dc. If, like a factory radio, your radio does not have a remote start output, then you can get the start signal from your vehicle’s fuse box. due to its low current draw, you can connect your ignition wire to almost any fused output terminal, like the one on the radio for example, as long as it only turns on when the vehicle is on. the use of an additional fuse connector plus a 2a to 10a fuse will facilitate this connection.

You will need to route the ignition wire to your amp through the car body; It’s often easier to route the power cable with the rca cables (next step), but you can also route it with the power cable after it goes through the firewall. the power and rca cables should run on opposite sides of the vehicle to reduce noise, but the low current of the power cable won’t matter.

step 8: make the signal connections

If your in-dash receiver has preamp (rca) outputs, connect your rca breakout cables to them. route the connecting cables to the opposite side of the vehicle from the power cable. it is important to separate the connection cables from the power cables as much as possible to avoid possible noise problems. now you can partially reinstall the radio in the dash. avoid completely reinstalling it if you can, in case you need to troubleshoot later.

If you are using a factory radio without rca outputs, you may be able to get your amplifier input signals from the factory speaker wiring. the speakers will get their signal from the new amp, leaving the radio’s outputs available to use for the amp’s inputs. there are two ways to do this: get a line output (loc) converter that will adjust the speaker level signal for your amp’s input, or get an amp with speaker level inputs. you cut the factory speaker wires behind the radio and connect the wires coming from the radio to the inputs on your locomotive or amplifier.

learn more about line out converters.

Step 9 – Wiring the Speakers

Now you need to provide a way to get the music from your new amp to your speakers. the best way to do this is to run new speaker wire from each amp output to each speaker. use 14 or 16 gauge wire for speakers, 12 or 14 gauge for subwoofers. speaker-level signals aren’t very prone to picking up interference, so it’s okay to run speaker cables close to power cables.

You will need to run each speaker wire in the door through the rubber gasket or boot around the hinge, to protect the wires from the weather or from getting caught in the door. there may be a molex plug or similar obstruction blocking the way, but you can usually find a place to drill a hole big enough to run the cable through. disconnect or cut the factory speaker wires and connect the new wires directly to each speaker terminal.

It is important that you maintain the correct polarity of the speaker wiring. this means that each positive terminal of the amplifier connects to a positive terminal of a speaker, and the same goes for the negative terminals. this ensures that your speakers work in mechanical phase (all speaker cones move in the same direction with the same type of signal) and will sound balanced when played together. The positive and negative terminals of each speaker should be labeled, but if not, the positive terminal will usually be wider than the negative terminal.

uses factory speaker wiring

Another, much more convenient way to send the signal fed from the amp to the speakers is to run the speaker wires into the harness behind the receiver, where all of your car’s speaker connections are accessible. In one single place. you cut each speaker wire from the receiver harness and reconnect it to a speaker wire coming from the amp. the signal can then flow from the amplifier to the speakers through the vehicle’s original factory wiring. this technique will work well in systems with up to 75 watts rms of power per channel, but for more powerful systems it may be better to run new speaker wire directly from the amplifier to each speaker.

see how to connect an amplifier to a factory stereo to see how it can be done.

step 10: connect all the cables

Carefully hang or trim each wire and connect it to the amp. make gentle bends in the cables, not sharp bends that can pinch. Many people cut small slits in their vehicle’s carpet and run wires under it, for discreet installations that look neat from the factory. a wiring snake is useful for this. Tape the wires to the snake, thread it under and through them to where you want the wires to go, and pull.

step 11: turn it on

Check all wiring, from the battery and receiver to the amp and speakers, making sure all connections are tight and secure, with no loose strands that could cause a short. especially check that the ground connection is firm and secure. set all amp gains to minimum and turn off all filters and any bass boost or eq you may have. check that the main fuse is correctly installed in its holder. then, reconnect your car’s negative battery cable.

turn on your car, then turn on the radio. check that the amp is on (there will probably be an indicator light somewhere). put on some music and turn up the volume just enough to hear. now check that the sound is coming from each speaker and/or subwoofer in your system. If all sounds good, you can finish reinstalling the stereo and all the panels on your vehicle, then continue to step 12.

step 12: setting the amplifier gain

Setting your amplifier’s gain, or input sensitivity, matches the amplifier’s input level to the receiver’s output level, resulting in distortion-free music and minimal background noise.

For a detailed explanation of how to do this, read our article on how to set the gains on a 4-channel amplifier. If you’re installing an amplifier for a subwoofer, read how to tune your subwoofers. the approach is the same, we have simply adapted the explanation to each situation.

enjoy your new system.

when things go wrong

Usually once you’ve installed your amp, you can turn on the stereo and immediately enjoy all the extra power and detail in your music. but sometimes things just don’t work out the way we hoped from the start. If this happens to you, don’t stress too much. Read our article on troubleshooting your amplifier setup for help finding and solving the most common problems.

call us: we will help you equip your system

your best first step is to call crutchfield and talk to a consultant about what your amp will need. they will make sure you get all the necessary hardware and accessories for a successful and satisfactory installation. And remember, anything you buy from Crutchfield comes with free lifetime technical support. just click “contact us” at the top of this page to get the toll-free number and other methods of contacting us.

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