2004 Chevy Blazer ZR2
December 2004
in my vehicle, so Plan A was to use an adapter that plugs into an
unused port on the back of the head unit, the same port that's used
for satellite radio and other remote sound devices. My Blazer didn't
come with any external audio devices, so I ordered up a Soundgate
adapter. That's all fine and good, but I figured why not go a step
further and add a Kenwood KAC-8401 4-channel amplifier and 3 pairs
of
speakers to upgrade the stockers? Now we're talking. And while I
was at it, I'd add an Infinity BassLink powered subwoofer to pump out
some bass.

Plan A got trashed when the Soundgate adapter didn't work. Never
did figure out exactly why, but the company's tech support guessed
that since my vehicle didn't come with any external audio devices, the
auxiliary input might not have been set up to work at all (the head unit
wouldn't detect the auxiliary input).

So I moved on to Plan B, which was this: a Sony CDX-F7700 head
unit with its own auxiliary input. I installed it with the Infinity subwoofer
and the three pairs of aftermarket speakers (the Kenwood amp was to
be eBay'ed, thanks to ridiculous mail-order restocking charges).
Worked fine and sounded pretty good until I realized that when the
door and dash speakers are wired together in parallel, the ohms went
from 4 to 2. Not good for the head unit...fortunately I didn't  push it
too hard. I tried running the dash speakers separately, then the door
speakers, but it didn't sound as good as when all 6 speakers were
going at once. So I moved on to Plan C.

Plan C was to use the Kenwood amp to power all 3 pairs of speakers.
Its four channels are capable of handling 2-ohm loads, and it pumps
out 60 watts RMS versus the Sony's 23 watts RMS. But where to
mount the amp? It was too big to fit under any of the seats, and I
didn't want it lying in plain view of would-be thieves (although the
Sony head unit and Infinity sub kinda make that a moot point). Also, I
didn't want to use up any more cargo space in the back of the Blazer.
I'd heard of guys putting amps in the small storage areas behind the
front seats, so that's what I did. It wasn't easy and it took a long
friggin' time, but here's how it went.
Above Right: To start with, I removed the rear passenger seat (six 18mm bolts;
deep socket required) and the lower interior panel. Not too hard.
Above Left: Naturally, the wiring is the worst part of the job. GM actually helped out
a bit by placing the carpet overlap under the rear seats (above, upper right in photo).
It was pretty easy to run the speaker wires and RCA cables across to the driver's
side, where all the audio cables were run (power wires run on passenger side).
--Amp goes here--
Above: Hard to believe all these wires fit inside the dash. I used a Metra installation
kit
with the pocket under the head unit. With the head unit placed higher in the
opening, it gets the rear of the unit up above the bracket thingie inside the dash that
often gets in the way (didn't have to whack it off).
Above: With the lower panel removed, now
the fun begins. The gray padding covers an
insert that serves as the small, oddly shaped
storage area behind the hinged door. It is
plastic-riveted to the panel and must be
removed.
Left: more rivets (small, bottom of
photo)
Above: I used a Dremel tool to grind off the
rivets. In theory, with a little help from plastic
epoxy the insert is still usable if I ever want
to put it back in (probably won't happen).
Here it is removed from the lower panel.
Above: Lower panel without the
plastic storage insert. You can see the
access door on the right (view is from
the inside of the panel). One question
that's come up over the years, from
others who have tried this, is what
happens when the cup holder support
is no longer there. The plastic insert
has a center column (part of its odd
shape) that provides support for the
plastic cup holders. With that support
gone, there's a little more "play" in the
cup holder, but it's still more than
adequate to hold a beverage.
Above: Now, back to the amp. This photo was after preliminary mounting. The red
wire is power for the Infinity sub; yellow wire on right is the remote turn-on wire for
the sub amp. I used a Tsunami amp wiring kit for the Kenwood amp, which includes
the 4-gauge ground wire and the blue 8-gauge main wire to the battery. It also comes
with an in-line fuse holder and some miscellaneous, helpful items. The amp isn't a
perfect fit, as the wheel well gets in the way a little. I had to use a couple of 3/4"
nylon spacers to get the amp to set out a bit. The pro installers (and the Kenwood
instruction manual) often recommend a plate to mount the amp on, but obviously I
didn't do this. I put rubber washers under the amp mounting holes to buffer things a
bit. Having an on-board fan in the amp helps, as there isn't a lot of air flow inside the
storage compartment.
Left: All wired up, with a little help
from duct tape (I love that stuff)
Right: With the lower panel installed. There's
still a surprising amount of space in there...not
sure why GM cluttered up so much of it with the
plastic insert (there's an identical space behind
the driver's seat.
And finally, my Sony CDX-F7700 head unit (with RCA inputs for my MP3 player):
Above: The RCA inputs are screwed into the Metra kit, so there's no fumbling around
with patch cords in the dash. Just plug and play! As I review this in May 2011, the
setup seems so quaint in this world of in-dash video, navigation and iPod docking
stations. But at the time, it was all I needed. The old Archos mp3 player I used to
plug into the head unit was long ago replaced by a smart phone.
Above: Here's the Infinity BassLink installed in the rear passenger-side cargo area. It
won't make your hood bounce, but it adds enough bass for me. It's compact enough
that almost all of the cargo area is still usable. The case is pretty thick plastic and the
speaker grilles are metal. The sub has taken some abuse over the years, but has
held up very well. I used sheet metal screws to secure the mounting brackets to the
floor. This location does get in the way of removing the plastic body panel (mostly
where it meets the tail gate); however, the panel can still be taken off with the
BassLink where it's at. When the internal amp failed in 2011, by some stroke of luck
I'd left just enough space between the sub and the wall to fit a small mono amplifier to
power the speakers externally.
Left: Passenger side door
with panel removed. Note
my stellar duct tape job
securing the crossover for
the Infinity Kappa 62.5i
speaker. Nobody will ever
accuse me of being a
professional installer. Duct
tape stickiness has a useful
life of about 5 years. After
that, things start to rattle a
bit.
I ran the battery wires for the
Kenwood amp (blue 8-gauge) and the
Infinity subwoofer (red 10-gauge)
through the radio antenna entry point
under the passenger side dash. I was
able to stuff the smaller red wire
through the same hole as the antenna
wire, but the blue wire needed its own
hole and grommet.
Here's how I initially mounted one of the
inline fuse holders. A few years later I
added a fused distribution block.
This was my first major sound installation, and it was kinda fun. Along
with the amp and head unit, I'm running Pioneer 4x6 plates in the
dash, Infinity Kappa's (2-way) in the doors, Infinity 6x9 Reference's
(2-way) in the rear, along with the Infinity BassLink powered sub. It
won't wake up the neighbors, but it's good enough for me.
Update March 2005

Well, I finally got around to installing the PAC SWI-X that's been
sitting in its package for about two months. This device allows an
aftermarket head unit to be operated by the steering wheel controls.
The concept is pretty simple - it takes the signals from the steering
wheel controls and matches them up with IR signals from the Sony
remote control. So it's basically a learning remote. Installation is a
little complicated to figure out at first, but eventually I got it right.

To start with, you need to have the radio out of the dash, so installing
the SWI-X while you're doing the head unit install works better. Step
1 is to figure out which wires in the factory harness are responsible
for steering wheel controls. The Blazer uses a GM24 wiring harness,
as identified in the Vehicle Connector Chart in the PAC instructions.
In the Vehicle Application Guide, the location of the steering wheel
control wires are listed as pins
A6 and A7:
cut the green wire and hooked it into the switched 12V main power
wire. That way, the steering wheel controls got their 12 volts. I also
cut the
blue wire and connected it to a longer wire that goes to the
SWI-X unit, so that it could receive signals from the steering wheel
controls. It gets a little confusing because the SWI-X uses a green
wire to receive steering wheel controls, whereas the green wire
coming from the steering wheel is actually the power wire. Also
required was a separate power wire going to the SWI-X so that it can
operate. I mounted the unit inside the CD holder console (see below).


I like this setup because it allows easy access in case I need to re-
program the unit. I drilled two holes in the plastic CD tray insert
(easily removable with just two Phillips head screws), a bigger one for
the group of wires on the right side of the unit, and a smaller hole for
the IR emitter wire coming out of the left side of the unit. I ran the
wires straight down the center of the console and up through the
back of the dash. Under the plastic insert seen below is a perfect
place to hook up the ground wire. There's a couple of nuts on studs
that secure part of the center console. Excellent grounding.
Look closely and you'll see where I mounted the IR emitter. It needs
an unobstructed line of sight to the IR receiver on the head unit. The
Sony unit receives its signals on the right side of the face, so I
mounted the IR emitter on the right side of the center console.

The best part about the SWI-X is that you can make each steering
wheel control do anything you want (within the limits of the head
unit's remote control). If you want the volume controls on the steering
wheel to scan for radio stations, make it so. Overall, a nice little
gadget.
Update Summer 2006

Sometime during the winter months I started noticing random static
and an occasional odd switch from CD to AUX or the
whole unit would
shut itself off. While checking for bad wires throughout the vehicle (no
easy task), I noticed that the static returned whenever I bumped the
center console. I traced the static to a loose ground wire for the SWI-
X. I'd attached the ground wire on a stud underneath the console,
and the nut fastening the stud (and ground wire) had come loose.
Took me about 10 seconds to fix and I had no other problems
after.

Update April 2007

With the addition of train horns in the Blazer, yet another fused power
wire was needed. Now with 3 wires connected directly to the battery
(power amp, subwoofer amp and air compressor), it was time for a
fused distribution block. I picked up a
4-position AGU power fused
distribution block
from Lightning Audio. Much, much cleaner!
Pin A7 is a blue wire that carries
the steering wheel control signals.
Pin
A6 is green wire that is the 12V
power wire which gives the steering
wheel controls the juice needed to
operate. The Crutchfield wiring
harness I got for the Sony head unit
doesn't supply power to Pin A6. So I
Plastic rivet --->
Wired for
Sound!
These types of projects usually
start out innocently enough. I
bought a new Chevy Blazer
that came with a fancy in-dash
6-disc CD changer, but no
auxiliary input for my MP3
player. I am wholly opposed to
carrying stacks of CD's with me
Update May 2011

While fooling around with my transfer case vacuum switch project, the
amp on the BassLink sub quit working. Just like the JBL powered
subwoofer I bought many years ago for my home stereo, the BassLink
amp started blowing fuses.  Internet research revealed that many of
these amps fry themselves, but I wonder if I somehow contributed to it
by not unplugging the battery when I dug into my dash for the
vacuum switch project. Either way, the BassLink was toast.

I could have bought a new one, but some of what I read suggested
that many of these on-board amps last for a much shorter time than
mine did. So instead, I ripped out the electronics inside the BassLink,
bought a Pioneer mono sub amp, and used it to power the BassLink
woofers.
Here's what I removed from the
BassLink. To get to all of this, I
had to remove the heat sink on
the back of the unit.  
I really wanted to discard the whole heat sink, but
it was easier to bolt on a metal plate to cover up
all those spaces left behind. I like tight bass and
wanted to preserve the acoustic suspension. I
also had to plug the holes on the left, where the
BassLink controls were located.
I chose a Pioneer GM-D8500M mono amp to
power the sub. It was reasonably priced and
compact.
The amp fit perfectly behind the
sub, screwed into the side wall. All
the wiring was already right there,
so it was basically plug-and-play.
Editor's note: over time, these Blazers become
less-than-water tight. One of the reasons I
believe GM included the odd-shaped plastic
insert was to prevent moisture from entering the
storage compartment. Looking back, I should
have done more to protect the amp from future
moisture (although through D
ecember 2018,
based on feedback from my nephew who now
owns the Blazer,
the amp seems to be holding
up just fine).