12. Secure the Harness
Examine the entire installed harness and use a generous number of tie-wraps to keep it from flopping around and getting chaffed. "Pay special attention to sources of heat," Overholser suggests. "Places where parts vibrate or any place where the harness could rub. The cheapest way to prevent damage from rubbing is to take some fuel or vacuum line and just slit it open and slide the wires inside to protect them."
13. Diagram Your Wiring
Lastly, take a few minutes to draw a simple wiring diagram. It doesn't have to have much detail. Include all the circuits, the color of the wires, where they go, and what they do. The pre-built Painless harnesses use wires labeled with their circuit use-starter, ignition coil, etc.-and these pre-marked wires are available through retailers.
Be sure to note any extra wires you strung to accommodate additions to the circuit. Keeping the diagram handy in a trailer or toolbox can save time and frustration at the track if electrical problems occur and you need to troubleshoot in a hurry.
Unless you run an auto electrical shop, about the only way you are going to get the quality of a professionally built wiring harness is to buy one.
If you run a Bomber, Street Stock, or Mini-Stock, chances are you probably don't have the budget for an eight-circuit race harness from Painless Performance or anywhere else.
But that doesn't mean you have to run something patched together that is a fire in waiting or something that looks like you built it on the way to the track. The off-season is the best time to tear into that wiring mess behind the dash and do it right. I built a six-circuit, fused system for a few dollars and it took only an afternoon to do.
First I determined how many circuits and switches I wanted. For the most basic of applications, the only switches you need are a main off-on switch, one for the ignition, and a push-button for the starter.
I figured six fused circuits would be more than enough to get power to the ignition coil, gauges, low oil pressure light, and tach. That left me with two circuits to be used as spares or as backup.
Here's what I bought and what it cost:
* Marine quality push-button starter switch: $4.99
* Two 50-amp off-on switches $9.98* Six-circuit fuse block: $12.99
* Fuses: $1.49* Push-on terminal ends: $1.99
* Screw-type terminal ends: $1.99* Assortment of shrink tube: $2.49
* 0.032 lead free solder: $2.99* Red warning light: $2.49
* Wire markers: $1.99* Package of rubber grommets: $2.19
* Liquid tape: $2.99
I had a supply of wire already on hand (I buy extra when it's on sale, so I always have some in the shop). You'll have to figure your own cost for wire. Remember, no one ever wishes for smaller gauge wire when circuits get hot on race night, so buy big.
Sketch out your own wiring harness needs before you begin, and then design the control panel on paper. If you have limited space, do a mock-up in cardboard or stiff poster board first.
Because the one I built wasn't designed for a particular car, I put everything to the right side, assuming the material to the left would be filled with gauges when installed.
I used a scrap piece of aluminum bent to a convenient shape. The bends put the switches within easy reach, and the fuse block pointed toward the passenger-side door, where it would be easy to check and swap fuses from outside the car. I added a piece of slightly U-shaped aluminum behind the push-button switch to make it stronger. Drivers with gloves can really push on that button when they are in a hurry or frustrated.
After that, I followed all of Dennis Overholser's suggestions: I used a wire stripper rather than a knife (or my teeth) to bare the wire, took the factory coverings off the terminals, crimped and soldered all ends, and then used heat shrink tubing to cover them. Whenever possible, I used screw-on terminals, then painted over the screws with liquid tape.