Wanting to add an additional power block...

[cowboy63645]

Well, as the title says, I am wanting to add a 6 circuit distribution block to the rear of the TB. The main reason I am wanting to add it is for the rear auxillary lighting, addition 12 volt supplies, etc. Would this be a feasable addition, or do the factory fuse panel's offer enough space to run this stuff? I was going to run a 4 gauge wire from the main battery back to the fuse block and add a switch panel to the rear as well for all the additions, so it is all in one area, instead of having to run from the front of the TB to the rear everytime something is needed. What are your thought's and opinions of this?

[Philberto]

Simplify your life... get the distribution block. I know I plan on running two distribution blocks (1 front, 1 rear) when I get my aux battery setup in and redo all my current wiring. Stick with a 2-gauge or thicker cable though... voltage drop is your enemy, and the thicker cable will help to minimize it.

[Zero]

i have thought about doing something like that as well. take a look at some of the kits from painless.

[The Roadie]

I posted a list of the circuits in the rear fuse block that actually get fed from the 125A Megafuse up front. Many of the rear fuses are there for convenience only, and are actually fed from one of the four ignition switch modes, and those in turn are fed from FRONT fuse block circuits.

From my post in the OS:

The wire size from the battery to the front fuse B+ bus is 19 square mm cross section, or 4 AWG equivalent. Then it goes through the 125 Amp Megafuse, and to a 13 sq. mm wire to the rear fuse block: 6 AWG. So GM fuses that 6 AWG wire at 125A.

The front fuse block runs most of the vehicle powertrain systems. Engine, starter, lights, horn, emissions. The rear fuse block has fuses for electric windows, door locks, sunroof, entertainment, Onstar, interior lights, gauges, power locks, HVAC controls, 4WD system, and so forth.

The subtle issue not generally known unless you're tracing schematics is that many of the fuses IN THE REAR FUSE BLOCK are not fed by the big red 6 AWG feed wire!

Many of the fuses are there for convenience only, or they deal with circuits being controlled or monitored by the adjacent BCM (body control module). But the 125 Amp fused 12 V feed wire only goes to fuses that feed items that require unswitched power.

Any items that need power switched by the ignition switch are fed by fuses in the rear that are fed by the ignition switch harness, which in turn is fed from a 40 A fuse in the FRONT fuse block. So that current isn't coming through the 125 A megafuse that feeds other things in the rear fuse panel. Other rear fuses are fed by other means as well.

A summary of rear fuse panel loads that come only through the 6 AWG feed wire by way of the megafuse:

Liftgate module (solenoid for rear glass and hatch)
Seat memory module
Overhead console - garage door opener / voice recorder
Onstar
Radio
XM
HVAC control module
Sunroof
Aux power outlets
Rear Blower motor (LWB)
Interior lights via BCM (courtesy and reading lamps)
Dimmable lamps (gauges, radio, switches)
Seat motors
Door locks and window motors
Parking lamps
Rear wiper
Backup lamps

Since the rear fuse block is also used by the XUV, which has a plethora of motors not in the other vehicles, I concluded the 125A Megafuse is oversized, so stealing up to an additional 40-50 Amps is possible by just tapping your sub-panel to the rear panel feed stud.

If you only want 10-30 A in a circuit, I'd recommend not adding a panel at all, but just stealing it via an Add-a-fuse gadget from fuse position #13, rated for 30A, and meant for the rear blower in an EXT/XL/XUV.

Relay socket #45 is also available to steal power from in the US, as it's meant for European Rear fog lights.

If you don't have a sunroof, position #20 is available, rated for 20A. #11, 20A if you don't have or use the Bose remote amplifier.

Any more questions - I have the shop manual and (currently) lots of time to look stuff up.

[cowboy63645]

Thank you for the info Roadie! Although later on down the road a winch, and dual battery system will be added, it looks like I can tap into the rear fuse panel and add a few extra's for now. I will be starting this little project soon (hopefully) and I will start a thread on it for anyone else interested in doing something similar!!