I would love to add on some lights, but I do not know how to run the wiring into the fuse block. Can anyone help me with this fundamental and and rookie question?
On my crazy projects, I don’t always do the prettiest work underneath the hood, always safe, but I don’t care what the stuff you can’t see looks like. So I hope this helps, and then it’s up to you how clean you want to do it.
On a lot of my projects, I’ve used those extend-a-fuse things that plug into a fuse slot and allow you to run another line off it. If you search your fuse block under the hood with a test light (10” of wire wrapped around a marker light bulb), some of the lines are hot all the time, and some of the lines are hot only when the ignition is on. Point being, if you’re running emergency lights, you may want them to work without the ignition being on. On the other hand, the flood lights and rotating beacon only work with the engine running, they eat so much juice they’ll kill the battery in 30 minutes (I have a quick disconnect key ring with an extra door key so I can lock the door with the engine running if I need to).
Now, having said that, a lot of the extra lights I play around with I don’t go to the fuse box. I tap them off existing light circuits: extra brake lights off the brake light circuit, extra floodlights out back off the reverse light circuit, extra marker lights off the parking light circuit, etc. Those circuits are usually pretty accessible by pulling out a front corner light or rear brake/tail light. One of the concerns with the newer trucks (I mean like after 92) is they started using smaller diameter wires with better corrosion proof connectors to save money. LED lights take very little juice, so you can splice them right into almost any light line that runs incandescent bulbs. But something like my halogen front facing floods, if you want them to go on with an existing light circuit, you’d probably have to run them through a relay. Explanation for another day…
I generally use the heat shrink crimp connectors. If I splice into an existing line, I cut it and strip it, and put both original ends into one side of the connector, and then the line I’m running from the other end of the connector, with an extra, smaller fuse in the new line. If there’s not enough extra length to do it this way, I simply use a 3 or 4” piece of wire as an extender on the original circuit, but I always keep the original circuit connected directly on one side of the connector. In addition to heat shrinking the connectors, I usually take a dab of silicone seal and rub it up & down the connector because the two lines don’t make a perfect heat shrink seal. I’m sure 2/3 of TRS will jump at this procedure, and insist the lines should be soldered with heat shrink covers. It’s the best way, but that can be pretty hard to do in some locations. Crimps work fine if you do them carefully. Always give them a tug after cramping. It’s worth it to buy a quality stripper/crimper tool, less than $15.
Of course the diesel already had two batteries. For The Missing Linc and for the Road Ranger, I added a second battery to both trucks. I use a deep cycle marine battery for the second battery. The second battery has to be grounded very well to whatever it sits in as well as the frame, and anchored well (no bungee cords). Both of mine are in the truck box behind the cab.
i connected the hot side of the batteries together from battery to battery with 10 gauge stranded wire, two strands twisted together (Craigslist). I twisted it by folding the wire in half at the right length (too long), clamping the loose ends into a vice, stretching it out straight, and use a screw hook in a drill to SLOWLY twist them together keeping tension on the length (practice with scrap). It ends up with a very nice twist you can handle like a single wire. My wire was the nylon coated stuff you pull through a conduit, oil and grease resistant. I also put a knife switch in that circuit at the second battery, mounted in something like a potato salad container so nothing can ground against it, and connect all my emergency lights to the spare battery side. That way, if I stop and don’t have the engine running, I could run all the emergency lights off the marine battery without draining my truck battery. Start the truck, close the knife switch, and it charges the second battery. I just ordered real battery disconnect switches I’ll mount through the side of the truck box so I can connect or disconnect the batteries without opening the toolbox. My batteries and marine batteries are $35 from the scrap yard, you just have to go often and keep your eyes open.
Doing the connections and mounting the lights isn’t too difficult, the hardest part of the job is running the wires under all the panels, under the truck, etc. etc. The biggest thing there is to make sure wherever the wires might rub, maybe in addition to wire loom, I use a piece of vacuum tube or such around the wire in any rub spot (split it, put it around the wire so the split is on the backside of the
rub point, and a few zip ties). No more than I use these things, that’ll last me a lifetime.
i’m also pretty brazen about just drilling holes through stuff if it’s not going to be seen in the finished product. Whenever I run a wire through a drill hole I use a little rubber grommet (you can buy a little box of a bunch of sizes on eBay for like $10) so the hole doesn’t cut the wire, I wrap some friction tape around the wire where it goes through the hole, or I use the vacuum tube trick or any combination thereof, and then still dab it on both sides with silicone to take the motion out of the wires/rub, especially if it’s something that goes from inside the outside.
Biggest thing there is knowing what’s behind whatever you’re drilling into so you don’t drill through into wires. A lot of times if I’m not sure, I will use a piece of copper tubing around my drill bit cut up to about a quarter inch from the tip, so once the drill punches through, it doesn’t drill into anything past that.
If one side or the other is hard to get to, you can go to your local dry cleaner and get an electrical snake. The dry cleaner calls it a wire coat hanger. Cut the hook off, straighten it out, and use needle nose or such to fold over one end in a very tight loop that fits through the hole (if necessary, make the hole bigger). Strip a half inch of the wire, fold it the loop, and then wrap it all with vinyl tape, just a little bit so it doesn’t come loose. Then, from one side or the other, you can usually push the coat hangers through to wherever you need to get to, and then grab it and pull the wire through behind it. Many many times, I make some custom bends in the coat hanger to get the thing to come out where I want it to come out. If it’s going past anything sensitive, make sure you take any sharp edges off the lead tip, or maybe fold that over crimped tight too so it’s a round end. If you do it right, the wires should just slide through easily. If you have to pull on the coat hanger with any amount of strength, the wire may be hanging up and being cut by whatever it’s rubbing against. Many times it’s as simple as a gentle just jerk in the wire hanger back-and-forth, or having someone help feed the wire from one side as you pull from the other side
Of course, do I have to say that you want to disconnect the battery anytime you’re doing this kind of stuff? I also test my circuits without simple test light or meter before I put any juice to them. I made up a couple of alligator clips on a 15 foot piece of 16ga lamp cord 30 years ago. I have a regular 12v marker light bulb that hooks into it so I can either check continuity or check if there’s power. About seven or eight years ago, I got smart enough to even put a fuse in the test line.
Adding the fuses is as simple as cutting the wire and crimping female bayonet connectors to each end, plug them into a blade fuse, and then wrap it with a piece of friction tape.
Sorry, I know I can go on forever. There’s a short YouTube video on just about everything I’m talking about here if you search for it, how to use crimp connectors, how to make a test circuit, how to tap in the fuse box, how to tap a line, etc.
Hope it helps!
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