DIY Electrical Junction Box

Now more than ever our motorcycles' electrical systems are becoming taxed. Our ever increasing demand for the latest gear and gadgets such as a GPS, heated grips, heated gear, radar detector, cell phone chargers demands additional wires and connections, and by the time we've added the electric coffee mug warmer, it can look like a rat's nest beneath your seat and behind your headlamp. AND, if you never bothered to wire in a protective fuse, it can also create the potential risk for power surges and blown circuits. BUT, it doesn't have to be this way...

Today, we'll walk through the construction of an electrical junction box for your motorcycle. For about $20, this assembly will enable you to safely route and arrange your wires in an organized fashion, and protect them with an inline fuse. This setup will not only protect you from power surges, but will keep you from forgetting to turn all that "stuff" off and cooking your battery, because we wire this setup to be turned on and off with the key! The entire procedure will involve a trip to your local Radio Shack, and about an hour or so to actually do the work. So, go get the stuff, grab yourself a beer and get to work!!!

First let's start with tools required:
• #2 Philipps HD Screwdriver
• Wire cutter
• Wire stripper (carefully used pocket knife is ok)
• Wire crimper or sturdy pliers
• 2-liter plastic soda bottle (optional)

Now, the bill of materials:
• 8-post Dual-Row Barrier Block (distribution block)
• 8-post Position Jumper Cut in half
• Red and Black 18-gauge Wire
• Green 18-gauge Wire (opt., subst black)
• 5 Female Spade Connectors to crimp on
• 1 Male Spade Connectors to crimp on
• 2 Large U-shaped connectors to crimp on
• Several Small U-shaped connectors to crimp on
• 12V 30A Automotive Relay
• In-line fuse with 20A Fuse (not always included)
• Quick Connects to splice into wire
• Small Zip Ties
• Electrical Tape

Begin the project by taking a look at the wiring diagram posted here to get a feel for how everything will go together.

1. Strip the both ends of the lead wires from the inline fuse. Crimp one of the large U-shaped connectors around one end, this will go directly to the positive post on the battery. Crimp one of the female spade connectors around the other end. Plug this female spade connector onto the relay post marked #87.

2. Remove the Dual-Row Barrier Block from the packaging and loosen (do not remove) the screws.

Remove the 8-post jumper from the packaging and cut it in half. This is usually accomplished by bending the metal to and fro until it breaks. Lay the barrier block in front of you oriented left to right. Take one half of the jumper you just broke off and secure it beneath the 4 adjacent screws starting with the screw at the TOP LEFT. Now, take the other half of the jumper you just broke off and secure it beneath the 4 adjacent screws starting with the screw at the BOTTOM RIGHT. Refer to the wiring diagram for the correct orientation of the jumpers.

3. Cut a length of red wire about 12" long, and strip both ends. Your length of wire may vary depending on how far the relay is to be mounted from the block. Attach a female spade connector to one end, and plug it into the post marked #30 on the relay. To the other end, attach a small U-shaped connector, or twist the wire and solder it. Then attach this other end to the POSITIVE side of the block as indicated in the diagram.

4. Cut a length of black wire about 18" long, and strip both ends. Again, your length of wire may vary depending on how far the block is to be mounted from the battery. Crimp one of the large U-shaped connectors around one end, this will go directly to the NEGATIVE post on the battery. Crimp one of the small U-shaped connectors around the other end, or twist the wire and solder it. Then attach this small U-shaped connector to the NEGATIVE side of the block as indicated in the diagram.

5. Cut another length of black wire about 12" long, and strip both ends. Attach a female spade connector to one end, and plug it into the post marked #86 on the relay. To the other end, attach a small U-shaped connector, or twist the wire and solder it. Then, attach this other end to the NEGATIVE side of the block also, as indicated in the diagram.

6. Finally, we need to draw power from a switched power source. I tapped into the power to the taillight for my power source. And conveniently, the wire to the taillight of my 1995 Triumph Trident was a regular-sized female spade connector. Cut two lengths of green wire (or marked black wire), one about 18" long, the other 6" long and strip both ends of each wire. To the 18" piece, attach a female spade connector to one end, and plug it into the post marked #85 on the relay. Take the other end of the 18" piece and twist one of the stripped ends of the 6" piece onto it. Now crimp a male spade connector onto the two wires you just twisted together.

Unplug the switched power source (or splice into the line). Here, it was the regular-sized female spade connector connected to the taillight. I had to remove my taillight to accomplish this part. Attach a female spade connector to the other end of the 6" piece of green wire, and plug it into the taillight. Take the male spade connector attached to the two green wires you just twisted together, and plug it into the connector you just unplugged from the taillight.

Voila! You now have switchable power. All you need to do now to add accessories is to take your positive and negative leads from the accessory, crimp small U-shaped connectors to them (or solder the ends), and attach them to the appropriate sides of the block. To better discern positive from negative leads, I went the extra step of marking the screws on the positive side of the block with a red Sharpie, and those on the negative side with a black Sharpie.

I have access to thin flexible plastic sheet stock as well. I used this to fold a protective layer above and beneath the junction box to protect the connections from possibly shorting out. The edges are open in order to route the wires. As a substitute, I would cut a rectangular section out from a plastic soda bottle measuring 4" x 10". Fold it in half so it becomes two 4" x 5" sections. Use this as a sheath for the box, and tuck the edges away from the fold under the igniter box.

I took it for a test run just the other day, and it works great! Everything switches on and off just as it should, and no more worrying about dead batteries!