Until an advanced alien species teaches humans how to transmit electricity through the air, without frying everything around it, electrical wiring is here to stay. That's not good news for the hoards of hot rodders that aren't man enough to route simple strands of copper, but companies like Painless Performance have made the process remarkably straightforward. While Painless has built its reputation on quality harnesses, switch panels, and wiring accessories for just about every application imaginable, it has recently developed a new range of products that help muscle car guys enjoy the perks of modern technology. We're talking about new standalone controllers for electronic overdrive transmissions, keyless entry systems, CAN gauge interfaces, and pushbutton ignition start systems. To find out how to hook up this trick new technology to your old-school Bow Tie, we had Dennis Overholser of Painless explain it all to us. Additionally, he offered countless tips on how to avoid common wiring mistakes and rig up a fail-proof electrical system.
Not many people look forward to wiring a car, but doing it right is imperative in terms of reliability and vehicle enjoyment. As with any DIY job, avoiding some common mistakes goes a long way in successfully wiring your project car. "It seems like common sense, but two of the most common errors we see is cutting the wires too short and not supporting the wiring harness adequately throughout the vehicle," Dennis explains. "If you let the wires dangle and don't take the time to tie the wires to firewall or frame, they can work themselves loose over time. Obviously, wires on the floorpan aren't going anywhere, but wires routed in the dash or the inner fenders need to be clamped down every 12-14 inches."
In extreme cases, wiring that's in poor health can lead to fires. In less extreme cases, bad wiring can result in everything from the improper operation of the radio, headlights, and gauges. According to Painless Performance, it's not at all reasonable to expect a wiring harness that's 40-plus years old to operate as if it's still new. "Using old wiring is a ticket to disaster. You have to assess the kind of condition the harness is in," says Dennis. "Exposure to heat, moisture, and salt can considerably reduce the longevity of wiring. Wires that are brittle or dangling can fail at any time. Sometimes the chassis and interior harness in an old car may still be in serviceable condition, but due to heat exposure the wiring inside the engine compartment is a complete disaster and needs replacement."
Poor ground wiring can create all kinds of electrical gremlins, and understanding why requires exploring the basic properties of an electrical system. "Electric current must make a complete circuit by flowing from the positive side of the battery, through the device it's operating, and then back to the negative side of the battery. If it does not make that complete circuit, electricity won't flow, and the device will not operate," Dennis explains. Consequently, the negative side of the electrical system is just as important as the positive side. "The main battery ground should go directly to the engine/transmission assembly for maximum efficiency. The engine should have a ground strap attached to the frame as well as the body. Some people don't use a ground strap between engine and body because they think that the motor mounts will provide adequate ground contact, but they don't. Without proper grounding, the gauges won't read properly and the overall operation of all the electrical circuits may be compromised. Make sure there is good contact, and also make sure the gauges in the dash are properly grounded as well."
To the average hot rodder, wires are wires and they all look the same. In truth, this is a foolish assumption to make, as the quality of material used to wire a car plays a dramatic role in safety, reliability, and the overall performance of the electrical system. "The Society of Automotive Engineers has developed a very strict system of standards for rating wires. Most wire imported from overseas is general purpose, or GPT wire," Dennis explains. This type of wire has a very low melting point and uses plastic insulation. High-strand cross-link wires—such as GXL, SXL, and TXL—have extra abrasion resistance and heat resistance properties. "Instead of using plastic insulation, they rely on a denser compound insulation material that's more like fiberglass. As a result, all XL-grade wiring has a much higher melting point with a temperature rating of -51 degrees to 125 degrees Celsius, which makes it ideal for high-heat areas like the engine compartment. TXL wire meets the exact same temperature rating of GXL and SXL wire, but because of its thin-wall construction it's the lightest and easiest to route throughout the car. That's why Painless Performance uses TXL wire in all of our harnesses."
As with wires, many people think all wiring harnesses are the same. According to Painless Performance, however, a vehicle's wiring harness can be broken down into three categories: the engine harness, the chassis harness, and the interior harness. While most Painless Performance harness are designed for the complete vehicle and include all three sections, certain applications only require a portion of a complete harness. The engine harness controls the engine functions—such as all the engine-related sensors and electronic throttle actuation—as well as most electronic transmission control functions. The chassis harness has circuits for all the headlights, taillights, turn signals, brake lights, horn, radio, A/C and other basic vehicle functions. Finally, the interior harness is usually part of the chassis harness, and it includes circuits for the gauges and indicator lights. The all-in-one nature of a complete vehicle harness can lead to some confusion for engine swappers. Since these applications often already have a chassis and interior harness, Painless Performance offers separate engine harnesses specifically for engine swaps. "All of our engine harnesses are specific to the engine and not the vehicle. This allows an engine, like an LS1, to be installed into almost any vehicle," Dennis explains. "In other words, the same exact engine harness you would use to swap an LS1 into a Camaro can be used to swap and LS1 into a Chevelle. Caution is always advised when transplanting a newer engine into a car that's already computer controlled. Different computers control different functions, like gas gauges, and may not be compatible with the new computer being installed. In these instances, we recommend calling the Painless tech line at 800.423.9696 to prevent potential headaches."
Safely Adding Accessories
Very few muscle cars left the factory with power accessories, but today's enthusiasts want the same level of comfort and convenience in their play cars as they have in their commuter cars. Since adding features like power door locks, power windows, stereos, and even GPS can lead to hacked up wiring, Painless Performance offers several products to ease the wiring process. "Each accessory circuit needs some kind of electrical protection, and it's always advisable to use a separate fuse block or circuit boss to reduce the potential for fire. Painless has several auxiliary fuse blocks, like the CirKit Boss, which are designed for adding circuits to any vehicle," says Dennis. "It includes an in-line circuit breaker, a relay, a fuse block, a pre-terminated wiring harness, and mounting hardware. Another nice feature is that it includes both constant and ignition-actuated hot circuits. If there is a spike in current, the CirKit Boss will overheat the fuse and open the circuit for an extra margin of safety."