Following are the images from installing all of the electrical components. Click on the thumbnail for a larger view.

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Getting organized is key, I laid out everything I needed and got started.

Project Table of Contents
1) Pre-Installation planning
2) Electrical Installation
3) Final mounts & demo video

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The first step was to disconnect the car battery. I’ve been using the positive terminal post right below the engine fuse relay center as a place to hook up my sub woofer amp. Now I’ll be adding another connection here that will go to the +12v lead of the P1900 power box.

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The next step was to remove the main center console bezel. With the bezel gone I could see how much space I had to work with, it was going to be tight vertically. I first needed to remove two metal brackets with screw holes used to help secure the main bezel. These brackets (one next to the yellow box and the other to the left, already bent up for removing) would be in the way of the rear of the HVAC controls, which would be relocated to the very bottom of the center console stack.

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While I went on to dance with the +12v power cables, my friend Michael used a metal grinding wheel on a Dremel to cut the metal brackets out to make way for the HVAC.

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Despite what they say about black cats, they actually are quite helpful when it comes to detailed electrical work.

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Running power cables through the firewall is usually a chore, but GM engineers apparently don’t mind a little smoke coming through since they left this handy large hole leading to the passenger foot well. The car battery has been removed, you can see the flat square tray it sits on. Behind that is ribbed tubing coming through the round firewall hole. This tubing contains the power cable for my amp, I’ll simply be adding a second power cable leading to the P1900.

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I needed access to the ignition wire harness so I removed the kick panel under the steering wheel. You need to pop out and remove the screw behind the fog light/trunk release buttons to fully remove the kick panel.

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Here you can see how deep the HVAC unit is. It’s actually a very compact, self contained unit. Pretty advanced for 1996 when it was originally designed.

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Here in the passenger foot well I’ve removed the hard kick panel that separates the passengers feet from a fuse box and integrated computer. Directly above (behind the glove box) I’ve pulled down the Sony AUX-300 auxiliary audio input box I’d installed years ago. The red cable is +12v already connected to the fuse panel post in the engine bay mentioned earlier. This end here will soon meet the P1900 to supply power to all of the new components.

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The large white connector, bottom left is for HVAC which I moved from the middle shelf to the bottom. It was also time to remove the Sony head unit from it’s top location, down one to the middle shelf.

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Here we’re under the steering wheel looking at the ignition wire harnesses. I’m looking for the +5v wire that will send a signal to the P1900 to boot the Mac mini when the car’s ignition is turned on. I had removed this harness once before, it’s the black one on the right.

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The +5v is the brown wire on the right. You can see the smaller blue wire stuffed into the brown’s slot, this is the power-on cable I previously installed for my sub woofer amplifier.

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It’s tight but you can squeeze the needed 12 gauge wire (in black) along with the brown and blue in the same socket of the wiring harness. In the background you can see the valet switch has already been connected to one side of this +5v wire and is running to the P1900.

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Soldering the black wire from the ignition harness to the other lead of the valet switch completes the valet switch installation. Fred provided a helping hand for the soldering work.

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In order to install the power button cable that came with the P1900, you have to open the Mac mini case. There aren’t any screws to remove, just wedge a thin putty knife along the sides and pry it open.

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The power button cable is a Y adapter. The base of the Y plugs into the main logic board and one branch connects to the actual power button cable, while the other branch connects to the supplied wire that runs to the P1900 (in grey on the left).

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The Carnetix P1900 has a half dozen or so settings that you can select via jumpers on the main board. Just follow the manual and choose the ones best for your situation.

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Preparing for the moment of truth, the first power on test. Before installing anything in it’s final location I wanted to make sure I had all the wiring correct.

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Success! The first power-on test worked without a hitch.

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Sometimes I even amaze myself.

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Since the wiring was correct, it was time to install everything in it’s new location. This is the rear of my Sony head unit. Once set of RCA cables carry the audio signal out to my amplifier while another set brings audio in from the auxiliary audio input box.

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In all of my research no one had mentioned exactly how they wired the LCD for power. Two power cables came with the Xenarc, one indoor AC power adapter and one DC cigarette lighter adapter. I wanted something cleaner than just plugging into a cigaret lighter so I cut the power cable and separated the two polarities. Barrel cables like this use the outside wire for negative and the inside for positive.

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I soldered the negative wire to a terminal loop that would be grounded to metal in the car, and the positive to an extension wire that would run directly to the P1900 and supply the needed 8 watts. Using a lighter I heated shrink tubing over all solder points.

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When I installed the Sony head unit years ago I had drilled a hole for a ground point in the metal frame of the center console. You can see the black screw holding several terminal loops including the newly added ground for the LCD. I ran the red positive power end towards the P1900, and the barrel plug (out of focus in the middle) sat waiting to be plugged into the back of the LCD.

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I cut a hole in the bottom of the glove box to pass all the necessary cables through to the Mac mini. From left to right: power button cable, Mac mini power, VGA, USB for the LCD, and lastly the 3/8 inch audio cable.

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Everything was starting to line up as I neared the home stretch. Since I knew I wouldn’t have time to begin the permanent mounting brackets I just needed a way to mount the head unit and LCD temporarily. I ended up using double sided tape to hold the head unit in place and used the right-angle mount that came with the LCD which I taped to the top of the head unit. It wasn’t pretty but it worked.

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The Mac mini fit nicely in the glove box. I put a 1/2 inch piece of soft foam (not pictured) under the Mac mini to help dampen vibrations.

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Why the foam still isn’t pictured…it’s hard to say. But you can see the green and black power button cable which I squeezed through the Mac mini’s air holes on the bottom so I could completely re-close the case and still connect to the power button extension cable coming from the P1900.

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Nothing quite as much fun as laying your ribs on the door sill of a car for two days straight. Ahh, good times.

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Everything was now mounted temporarily and ready for real usage. You’ll notice I left the protective film on the LCD while working just to help keep it clean and undamaged.

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All finished up and ready to go. That is until I get around to making the real mounting brackets for the LCD and head unit.

Audio Quality Issues
After the installation was complete I spent some time tuning the iTunes equalizer to optimize audio quality. During this time I noticed there was a fair amount of noise coming through the audio feed. It was a pulsating hum that fluctuated with the hard drive accessing in the Mac mini. This is typically caused by ground loop noise where electricity that should be grounded to the chassis of the car finds a faster path to ground by going through your audio cables. It’s common when your actual ground isn’t efficiently grounding your system and electricity is lazy like the rest of us and takes the easy way out. After driving around a bit and re-testing my grounds I determined that the grounding problem was not in my power cables but simply caused by the design of the Mac mini allowing an easier path for the electricity via the 3/8″ audio out cable instead of it’s power cable. There are a number of solutions out there to solve this, but the easiest and most effective in my case was to purchase a Ground Loop Isolator from Radio Shack. Sadly this problem also occurs in some other Macs, including my G5 at work. Installing the ground loop isolator removed about 90% of the hum which was enough to make it inaudible while driving.

Day to Day Use
After driving around for a day or so with the completed system in place a few things rose to the surface which needed tweaking.

First was an oddity, every time the Mac mini booted the system volume level was set to 50%. I wanted iTunes volume and the system volume set at 100% all the time in order to provide the right volume control on my head unit. With both of these volumes at 100%, the volume control on my head unit was a normal ratio of graphical bars to decibel output. With the Mac mini’s volume at 50% however, I had to crank the head unit volume to reach listening levels. This Apple knowledge base article confirms that it’s a real bug and there’s no permanent solution. Until Apple provides a fix, I have this AppleScript launch at startup which sets the Mac’s volume to 100%.

Next, I quickly found that the shutdown process was annoying and lengthy. As I mentioned earlier I’m choosing not to sleep the mini every time the car is turned off, so that means when the ignition is switched to off, the P1900 sends a sleep command to the Mac mini which the mini ignores as specified in the System Prefs “Allow power button to sleep the computer”. At this point the P1900 is going to kill power to the mini in 60 seconds, so I need to manually shut down the computer within this time. Going to the Apple Menu and the selecting the tiny “Shutdown” command wasn’t easy, so this simple AppleScript in the dock allows for a single tap on the LCD to turn off the computer before the P1900 stops providing power.

Continue to part 3: Final mounts and demo video>

Project Table of Contents
1) Pre-Installation planning
2) Electrical Installation
3) Final mounts & demo video