2004 Chevy Blazer ZR2
December 2004
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.
To start with, I removed the rear passenger seat (six 18mm bolts;
deep socket required) and the lower interior panel. Not too hard.
--Amp goes here--
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).
<----- 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).
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.
<--- more rivets (small, bottom of photo)
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.
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.
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.
<--- All wired up, with a little help from duct tape
(I love that stuff)
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):
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.
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.
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:
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 here 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've had no other problems since.

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 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 like this:
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 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
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 May 2011, the amp seems to be holding up just fine).