How to install a car stereo, a step-by-step guide

Tools

Unfortunately, what you'll need and the steps required will vary not only from vehicle to vehicle, but also between different stereo units. That said, though, the basics are generally the same.

For your average installation, you'll need these tools as a bare minimum: a wire crimper/stripper, a socket wrench (not pictured), a flat-head screwdriver and a Phillips-head screwdriver.

(Credit: Derek Fung/CNET)

Harnesses

You'll need to purchase an audio wiring harness that suits your make and model of car. The harnesses on the left fit our demonstration car, a 2004 Toyota Corolla.

(Credit: Derek Fung/CNET)

Joining wires

You'll need some way to join bare wires. For this step-by-step guide, we'll be performing a temporary install, so we'll be using electrical tape (top), although twist caps (bottom) are another good option.

We'd recommend doing a temporary install first to confirm that everything works. Once that's been done you should uninstall the stereo and make things permanent by soldering all the connections together.

(Electrical tape image by Allen Pope, royalty free and Antuan Goodwin/CNET)

Step 1: strip

The first part of the installation, connecting your wiring harnesses, ideally takes place outside of the vehicle.

Start by stripping the ends of the wires on your vehicle's wiring harness, leaving about a centimetre to 1.5cm of exposed wire. This is done by inserting the wire into the stripper at the appropriate gauge, twisting the stripper to bite into the insulating jacket, and then pulling to expose the copper wire.

(Credit: Derek Fung/CNET)

Step 2: strip again

Once you're done with the vehicle's wiring harness, you'll want to repeat for the receiver's harness. The wires are coloured with a universal code: red for power, yellow for memory power, black for ground and orange for illumination. While the green, grey, purple and white wires are for the four speaker channels.

(Credit: Derek Fung/CNET)

Step 3: not everything needs to be stripped

Depending on your vehicle's set-up, you may find that you won't need to connect all of the wires on the harness. In particular, you'll want to pay attention to the "blues". One controls the power antenna, the other turns on an external amplifier. Our vehicle isn't equipped with either, so we shouldn't even bother stripping them.

If you have stripped an unneeded wire, just cover the stripped end in electrical tape to be sure, to be sure.

(Credit: Derek Fung/CNET)

Step 4: twist and shout

With both wiring harnesses stripped, it's now time to start making your connections. Begin by finding the red power wire on the vehicle's harness and matching it to the red power wire on the receiver's harness. Twist the two connections together as shown in the photo.

(Credit: Derek Fung/CNET)

Step 5: join up

Cut a long strip of electrical tape, place one end on, say, the vehicle's end and begin rolling it over to the stereo's end. Press down on the electrical tape to ensure that it has firmly adhered to both the insulating jacket and the bare wire connection. Give the newly joined wires a firm tug to make sure they're properly stuck together.

To avoid confusion, start by pairing and joining the big three power cables — red (power), yellow (memory) and black (ground) — before moving on to illumination (orange).

(Credit: Derek Fung/CNET)

Step 6: gimme some sound

When it's time to connect the speaker cables, pay close attention to the markings on the insulating jacket. Each speaker has two wires with two poles: a positive and a negative. The negative pole is usually marked with a black stripe. Make sure that you connect the positive cable on the car's harness to the positive cable on the stereo's harness; the same applies for the negative cables.

Connecting a speaker backwards puts it "out of phase" with the rest of the speakers in the set, causing it to pull air while the others are pushing. This essentially cancels out the sound and results in lower sound quality and volume. So, double check your poles before you make your connections.

The four pairs of speaker cables are coded thus: white (left front), grey (right front), green (left rear) and purple (right rear).

(Credit: Derek Fung/CNET)

Step 7: time for a surf

With your wiring harness completed, you can now begin to think about mounting it in your car. First, though, you'll need to know how to remove your car's current stereo. The best resource for this is the internet. Type your car's make, model and year along with "stereo" and either "replace" or "remove" into your favourite search site and you will be greeted with plenty of hits. Most of these will be for threads on enthusiasts forums.

The more popular your model, the more likely you'll find instructions on how to remove and replace your car's stereo. Printing any threads with step-by-step instructions and photos of the process is a good idea. And don't forget to bookmark any helpful threads too — if you have any troubles with your install, the guys and girls on these threads should be your first port of call.

(Credit: Derek Fung/CNET)

Step 8: disconnect the battery

Now that you're armed with instructions on how to replace your car's stereo, it's finally time to head on over to your car and remove the current stereo. First things first, though, disconnect the car battery, so you won't fry either yourself or the car.

Before disconnecting the battery, write down any security codes or settings for other devices that will lose power, such as alarm systems.

To disconnect the battery: pop the bonnet, use a socket wrench with a 10mm socket, loosen the nut on the negative terminal's connection and then pull the connection free.

(Credit: Derek Fung/CNET)

More than meets the eye

Despite having a discrete stereo, our Corolla is like most modern cars: to replace its stereo requires unfastening various, seemingly unrelated, pieces of trim, like the air-conditioning panel.

The next few steps will give you a flavour of what you'll need to do for most modern cars. If you find that these steps aren't applicable to you, however, please skip to step 14.

(Credit: Derek Fung/CNET)

Step 9: remove gear lever trim

With our Corolla, the first items on the agenda are to remove the ashtray and then to remove the plastic panel surrounding the gear stick. Most car trim bits and bobs can be pried off with a flat-head screw driver. If you're concerned about leaving scratch marks on the plastic, put a layer of electrical or masking tape on the screwdriver's tip.

(Credit: Derek Fung/CNET)

Step 10: taming of the hidden screw

To pull the air-conditioning panel free, remove the screw that's hidden between the fan speed dial; the dial itself is easily removed with a gentle tug.

(Credit: Derek Fung/CNET)

Step 11: come to papa

Jamming our flat-head screwdriver into its sides we levered the panel forwards. After a bit of prying, two rectangular gaps at the top are revealed. Wedge the air-con cover even further forward by putting the screwdriver into those gaps and levering away.

(Credit: Derek Fung/CNET)

Step 12: snap, crackle, pop!

Once the two gaps at the top air-con panel are exposed enough, stick your fingers in, grab the panel and yank it forward. Like most large pieces of trim, the air-con panel is held in firmly in place by a set of plastic plugs and requires a firm hand to unfasten from its moorings.

With air-con panel out, the air vents surrounding the stereo head unit can now be pulled out.

(Credit: Derek Fung/CNET)

Step 13: a long way to bolt

Now we can finally get at the stereo itself. In this model Corolla, the head unit is held in place by two bolts (the leftmost and rightmost ones in the picture above). These can be removed with a 10mm socket and can only be accessed with the aid of a 30cm socket wrench extension.

(Credit: Derek Fung/CNET)

Step 14: free at last!

Easing the head unit out of its portal, we can see that it's attached via a wiring harness — in the case of this Corolla, the harness comes in two parts (centre and right) — and an antenna cable (left); unplug both of these.

Don't throw the stock unit away just yet, you may want to re-install it when the time comes to sell your car.

(Credit: Derek Fung/CNET)

Step 15: harvest time

Because we're replacing the Corolla's standard double DIN stereo with another double DIN stereo, we'll need to harvest its mounting bracket that came with it for use with our brand-spanking new stereo. Simply unscrew the bracket using a Phillips-head screwdriver and attach it to the new stereo.

(Credit: Derek Fung/CNET)

Don't get screwed

(Credit: Antuan Goodwin/CNET)

Step 16: wire it up

Locate the wiring harness you built earlier and connect the vehicle specific end to the vehicle's connector, then plug the stereo's end in (bottom right). Don't forget to reconnect the antenna (bottom left) as well.

As our replacement stereo, Pioneer's AVIC-F310BT, does more than play tunes, there are lots of extra cables that need to connected. In this case, there's the GPS receiver (top left), Bluetooth hands-free microphone (centre) and iPod/USB connector (bottom centre).

(Credit: Derek Fung/CNET)

Step 17: everything in its right place

GPS antennas, iPod connectors and microphones all need homes. iPod and USB connections are easily threaded through various cavities into a car's glovebox. For satellite nav units, it's best that the supplied GPS antenna has a view of the sky, so a spot near the base of the windscreen is best. Mind you, if you want to hide unsightly wires you will probably need to remove various bits of trim, like the air vents for the windscreen.

Likewise, it's easy enough to attach the Bluetooth hands-free system's microphone on either the steering wheel column or windscreen pillar, but stuffing wires away out of sight, out of mind will take a bit of time as various plastic bits are removed and put back in.

(Credit: Derek Fung/CNET)

Step 18: user acceptance testing

Before sliding the unit into its hiding hole, tuck the wires away as best as you can; tying them in place with zip ties can help lessen the strain on the connections.

Prior to buttoning everything up, reconnect your battery and crank the vehicle up to make sure that everything works. Pay close attention to the audio, making sure that it sounds right and fiddle with fader and balance settings to confirm that audio is coming out of the correct speakers.

(Credit: Derek Fung/CNET)

Step 19: put Humpty back together again

Put the car's bits and bob back into place in the reverse order to which they were removed.

As you can tell, in the picture above, the blanking plates we've ordered for our vehicle haven't arrived yet, leaving a rather ugly gap either side of our new stereo. In the meantime, we'll just assuage our aesthetic pain by cranking the volume up.

(Credit: Derek Fung/CNET)

Tip 1: face off

Here are some further tips that may come in handy when installing a car stereo.

If your receiver features a detachable faceplate, now would be a good time to remove it. Not only will you avoid scratching the screen, but doing so will also make the installation easier.

(Credit: Antuan Goodwin/CNET)

Tip 2: bracket required?

Depending on your situation a new mounting bracket may be required. For instance, you'll more than likely require one if you're trying to fit a single DIN stereo into a double DIN hole, while some cars require new mounting brackets for third-party stereo head units.

(Credit: Antuan Goodwin/CNET)

Tip 3: roll up yer sleeves

If your new receiver came in a metal sleeve you may or may not need it. Again this depends on the mounting bracket being used and your car.

(Credit: Antuan Goodwin/CNET)

Tip 4: which holes are best?

There are many holes on the side of the receiver to accommodate many brackets and mounting options. Try to use one as close to the front as possible and another as close to the back as possible to promote stability. A wiggling receiver causes skipping CDs or, at worst, damaged internals.

(Credit: Antuan Goodwin/CNET)