Releasing the old head unit
The first and often the most difficult stage of
installing a new head unit is to release the old one from
its mounting. There are catches on the head unit that need
to be released, after which the head unit will slide out.
The way in which you release these catches depends on the
car, but it will usually involve the insertion of some
remove keys into the head unit. There are various different
removal keys for different head units, but in general there
are two main types.
ISO Removal Keys |
The first type, often called ISO removal keys, is four
prongs that are inserted into four
holes around the edge of the head unit. They are just
pushed into the holes to release the catches and then the
head unit can slide out.
The second type are flat pieces of metal that usually
slide in on the side or the underside of the head unit in
two small slots. There are several different variations of
this type of key, although often getting the exact one
designed for your vehicle is not necessary, as they are all
similar.
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European Removal
Keys |
If you don't have the removal keys, often a main dealer
for your marquee of car will release the old head unit for
you for free, as its only a one minute job with the correct
tools.
Disconnect the wiring
Once the head unit has started to slide out, you need to
leave it in place, as there will be lots of wiring attached
to the back of it. It is recommended that you disconnect
the negative terminal of the battery before disconnecting
this wiring. The negative terminal will be marked in black.
Depending on your car, it will usually just require the
loosening of one nut before it pulls off.
The next stage is to go back to your head unit and slide
it out enough to enable you to disconnect the wiring.
Although there are lots of wires, all the wires except for
the aerial are connected in two big blocks called the ISO
wiring harness. You need to disconnect these two blocks by
unclipping them, and then pull the aerial out of the back.
The aerial is usually a fairly thick black cable. Note that
some cars, particularly cars built in the early 90s or
before, do not have a standard ISO wiring harness.
If this is the case on your vehicle, you will require an
adapter harness. The installation process is the same,
except once you have unplugged the old head unit's wiring,
you need to plug the wiring harness in to the car's wiring,
inorder to convert it to the standard ISO specification.
Replacing the metal sleeve
The final stage of removing the old head unit is to
remove the metal sleeve that it was sitting in. These
sleeves have metal tabs (small bendable bits of metal) that
are bent down to hold the sleeve in place. To remove the
sleeve, find all the tabs that are bent down, and bend them
back up. Once all the tabs have been raised, the sleeve
should slide out easily. Remove the sleeve, then replace it
with the sleeve from your new head unit. Bend several tabs
down on the new sleeve to secure it in place.
Connecting the new head unit
Now you are ready to connect all the wiring to the new
head unit. There will usually be one connector for all the
wires except the aerial. This will plug into the back of
the head unit, and give you the two ISO blocks for you to
plug you're car's wiring plugs into. Once you have
connected these, plug the aerial in. On some cars, you will
find the aerial cable will not fit as it has a spiked
connector instead of the small round hollow connector used
by most head units. In this case, you would need a small
adapter plug.
Finalising the installation
You can now slide the head unit back into the
sleeve until it locks into place. Before doing so, you
should try to position the wiring you have just connected in
such a way that it will not be crushed by the head unit, and
will not prevent you from sliding the head unit fully into
the metal sleeve. The head unit should slide in easily all
the way. If it will not, slide it back out and reattempt
to position the wiring until the head unit slides
back easily. Once the head unit is in place, you can clip
the plastic trim on if one was supplied with the head unit.
You are then ready to reconnect the battery and test the
installation.
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