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DIY Auxiliary Fuse Panel Powers Accessories

Posted in How To: Electrical on September 11, 2019
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Automotive electrical is unmistakably important when it comes to the function of our rigs, but it's sometimes not given our best attention. We get the hard parts installed, maybe sling in some wiring between power and switches, and then call it a day.

In our case, we had added some accessories over the years and had a handful of inline fuses for those items hanging off the battery under the hood. We'd not had a failure due to the casual fuse wiring, but decided it was time to clean up our electrical additions. We opted to use an auxiliary fuse panel from Painless Wiring to consolidate all our underhood accessory fuses. Painless offers several configurations to accommodate a given number of circuits, switched ignition circuits if needed, and waterproofing. You can choose a size that works best in your rig, or combine kits if you need even more elaborate power feeds.

We mounted the company's seven-circuit, waterproof panel in a spot under the hood of our truck and used it to rid ourselves of all of the inline fuses we'd been using. The kit provided the feed wire to run to the battery, a main circuit breaker, and the wiring from each of the seven fuses. It's a fairly straightforward installation and provides a good opportunity to efficiently route your wiring and protect it from the rigors of temperature extremes and vibration. The result is tidy, reliable power distribution.

Over the years we had added several inline fuses for accessories on our truck. In retrospect it would have been smart to have used an auxiliary panel from the start. In fact, without labeling, we had somewhat forgotten which fuse went to which accessory, so we had to do some electrical sleuthing during this project.

Here's one thing to note when doing this type of wiring. Since the same current flows around the entire loop, both positive power wires and ground wires must be sized to accommodate the current draw of the device. If a single wire is used to connect several devices to ground, then that wire must be of sufficient size to support the sum current flow of all devices. On most vehicles, the frame and body are tied to battery ground and serve as a large return ground path.

We also can't stress enough the importance of making reliable connections. In fact, in most automotive harnesses, the connectors/connections are the weakest link. Second in line of failures is most likely wire damage or wire shorting due to abrasion of wire insulation, resulting in the wire itself shorting to adjacent exposed metal. In the high-vibration environment that exists in our rigs, it's good practice to add protective covering and stake down wire bundles to keep them from flopping around.

In addition to the wired fuse panel, the Painless Wiring kit includes mounting hardware, a 50-amp self-resetting circuit breaker, and a variety of connectors to aid in installation.
There are times when you may want to thread wiring though a framerail or other structure. We've used drip-irrigation tubing to help with this. It can help push the wire where needed and serves as protection once in place. We use this tubing to protect blue ARB air lines as well.
We like using these military-style battery terminals. They mount solidly and make adding terminal connections convenient and reliable. We often run a Group 34/78 battery and wire our winch cables to the side terminals, and everything else to the top posts.
With the wiring complete, we covered most everything using high-temp split-loom tubing to add a layer of protection against abrasion. An alternative is the use of Painless PowerBraid, a nylonlike split braided tube.
Proper wire strippers and crimpers help make solid wire joints. Crimping automotive wiring can make completely reliable connections, if done properly. The auto manufacturers all crimp connections, but for the best connections that withstand aging, moisture, and vibration, a proper crimp is needed to fully mate the wire to a terminal.
We mounted the 50-amp circuit breaker with cover along the inner fender near the battery to protect the main power feed running to the new fuse panel. The terminals provided in the kit can be crimped and have heat-shrink tubing to seal the connection.
If you have ever scratched or cut your arm on the sharp end of a trimmed zip tie, you know why we recommend picking up a set of flush cutters. They are designed to trim the tie close and leave no protruding end.
When doing harness work, we often work from the main wiring source outward. We'll use small zip ties to organize the harness as we go. They are easily snipped off and replaced as you revise the wire routing. This can also be a good time to take notes of wire color and routing should you need to troubleshoot some electrical malfunction in the future.
We fabricated a simple sheetmetal mount to bolt the new fuse panel in a spot high on the firewall, a place that should be fairly well protected from the elements. Painless provides spacers so the panel can easily be mounted to most any flat surface.
Inside the waterproof top cover is a label so you can record the device each fuse services. It's really handy being able to write in which fuse controls which device.
Here's a rear view of the fuse panel. It comes fully assembled with all wiring, and the connector pockets have been sealed to keep out dust and moisture.

Sources

Painless Performance Products
Ft. Worth, TX
800-423-9696
http://www.painlessperformance.com

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