Wiring Your C1 Corvette the Right Way
Wire It: Some special tricks for Corvette wiring
Gerry BurgerWriter
Wiring. The very term strikes fear into the minds of many Corvette owners. It’s true, wiring a Corvette brings with it a few special hurdles, but with the proper components and some patience, wiring a vintage Corvette is well within the reach of your average enthusiast. As a matter of fact, you may find a task that once caused an anxiety attack can be rewarding and fun—yes, fun.
There are any number of quality wiring kits on the market today ranging from exact reproduction harnesses for that 100-point restoration to the modern electrical kit that features extensive use of relays and a much superior ground (-) and fuse systems. We can provide two pieces of advice. One, if your vintage Corvette is 50 years or older it needs to be rewired. Period. Two, unless you are going for the aforementioned 100-point restoration, use a modern system. Modern wiring includes a much more comprehensive fuse system, utilizes relays to minimize load on switches and is much more versatile for adding things like air conditioning, high-end stereo equipment, power windows, LED lighting and the list goes on.
When it came time to install a modern electrical system in our 1960 Corvette project we opted to use the Ron Francis Wiring kit designed for early Corvettes. Our order also included an extensive grounding (-) kit that will ensure good connections from the headlights to the taillights and everything in between. The wiring kit is capable of integrating our Vintage Air air-conditioning system with ease, not to mention the Powermaster 120-amp alternator supplied with our Billet Specialties TruTrac accessory drive system. The ididit steering column includes all new turn signal switches and a horn switch. Simply include that information when ordering your wiring kit and the proper plug is supplied, it couldn’t be easier. The final major electrical component on our project car is the dual-quad FAST EFI system. It looks like dual-quads, runs like EFI. Happily, the Ron Francis panel was ample for everything we were using on the car. Regardless of which company you chose for wiring, it is a good idea to list your major components when ordering so the supplier will be certain to configure the kit to your needs.
While the alternator supplies power for all of the electrical needs when the engine is running, when it comes to cranking the engine and electrical needs when the engine is not running, you will need a good battery. From the very beginning of this project we knew there was only one battery for this car: a RedTop Optima battery. Great power, long life and all wrapped in a very attractive package, what more could you ask of a battery.
The first step in custom wiring is component location. Switches, horns, lights, stereo, air conditioning and all electrical devices should be mounted. If you are wiring a pure stock car these items are all predetermined, as is the location of the electrical panel. In a custom installation the main panel can be located almost anywhere from the trunk to under the dash (engine bay is not recommended). We mention the mounting of all components from experience. Our first choice for panel location was the passenger-side upper kick panel. It seemed like the perfect spot for the panel, with ample room and a direct shot to the battery, starter and our FAST EFI computer. We even went so far as to fabricate a bracket to mount the panel, then we thought it might be best to test mount the Vintage Air A/C system. Well, as it turns out the underdash A/C unit occupies the passenger-side kick panel. Luckily, we had not begun wiring. We fabricated a similar bracket and mounted the panel in the driver-side upper kick panel. Our Ron Francis kit had plenty of wire so the new location was not a problem, although the steering column made it a bit more difficult to reach things.
The Optima battery fit perfectly in the stock location (passenger-side wheelwell) and we had our Classic Instruments gauges mounted in the dashboard along with a reproduction ignition switch. We decided to use the light switch supplied with the wiring kit, along with the new dimmer switch located in the original location. Since we are running Hella halogen headlights we opted for a headlight relay and we were pleased the Ron Francis kit handled our LED turn signals perfectly.
The actual wiring is very straightforward, and with the comprehensive instruction book it is a simple matter of running the wires from the appliance (headlights, electric fuel pump, radio, wipers etc.) to the panel. The wires are all marked with their mission (e.g., headlight high beam, low beam, taillight, A/C feed and the list goes on). The kit does everything possible to minimize the potential for errors. Not only are the wires marked, they’re also color-coded to the panel. All the required connectors were also supplied with the kit.
While we did not use power windows in our car we did have the halogen headlights, LED taillights and our custom LED backup lights. The backup lights are easily controlled by the Lokar shifter module on our 700-R4 transmission. This module also illuminates the Lokar gear indicator panel.
The Ron Francis ground wire (-) kit provides a vastly superior system to the minimal effort made by the factory in 1960. With individual grounds for most appliances you are sure to have the proper power supplied to these components. When we had the body off the frame we welded four different stainless steel pads in the frame. The 1/4-inch stainless steel pads were drilled and tapped to accept 1/4-20 stainless steel bolts. We used these pads as junction blocks and to ensure an excellent ground through the frame. One pad was located on the driver-side front framerail, a second located on top of the frame by the starter/battery and the final two were welded inside each rear framerail. This proved to be a worthwhile modification and the stainless steel pads and stainless steel bolts ensure no unwanted resistance from rust.
It also should be noted that modern fuel injection requires extremely “clean” signals. Our FAST fuel injection system specifies a direct connection to the battery for both the positive (+) and negative (-) connections. We had mounted the FAST ECU on the passenger-side inner fender panel so it was a straight shot to the Optima battery. Since these EFI connections do not go through the master panel they include an inline fuse to protect the circuit and the computer.
While we hear of people wiring cars in a weekend, we spent several days on the project. This included routing the wires, modifying the headlight switch to accept the Corvette knob and other custom details. We also spent a lot of time securely mounting the wires and making sure they were all out of harm’s way. Grommets were used throughout the wiring process and in the end we were very happy with the system. We were more than pleased when we connected the battery cables and all systems worked as expected, not a single wire required changing, a benefit of taking your time with a quality kit. Similar results are available to any Corvette enthusiast that has some patience and can follow instructions.
One final word of advice, you may want to enroll in a Yoga class a few weeks prior to wiring a C1 Corvette because getting up and under that Corvette dashboard definitely requires a whole new level of flexibility.
01.A modern wiring system incorporates more fused circuits enabling you to have such modern conveniences as A/C, stereo, power windows and modern lighting. We mounted our Ron Francis panel up high in the driver-side kick panel.
02.The panel is color-coded and labeled, and the wires are color-matched to the panel. We like the concept of routing wires from the appliance (taillights, radio, wipers, etc.) to the panel as it allowed us to harness wires as we saw fit.
03.OK, at first glance these bags of wires and connectors may be a bit overwhelming, but fear not. Each bag is clearly marked and the instructions sequence the bags in an orderly fashion. It really is simple, one wire at a time and before you know it the job is done.
04.Our FAST fuel-injection system required “clean connections” direct to the battery. The FAST wiring harness was easily used alongside the Ron Francis wiring.
05.Likewise, things like the Classic Instruments speedometer module was mounted prior to wiring. The Classic Instruments gauges are prewired with plugs, while the 12-volt power comes from the Ron Francis panel.
06.Vintage Air A/C is another major component to be mounted prior to wiring. Once again, Vintage Air controllers are largely plug-and-play and are easily integrated with the main wiring system.
07. While the alternator provides power when the engine is running, it takes a battery to start the car and support electrical things like clocks and radio memory while the car is off. To that end there simply is no better choice than an Optima battery.
08.Prior to starting the car we used an Optima battery charger to bring the RedTop to full charge. This charger will also come in handy as we will leave it on the car if it is going to sit for long periods of time.
09.The Optima RedTop fit perfectly within the confines of the stock C1 Corvette battery location, which is in the passenger-side wheelwell.
10.We also mounted the FAST E6 ignition module prior to the start of our wiring project. The module arrived in a nice bright-red anodized finish but we opted to paint it semi-gloss black and sand the fins to aluminum for a more subtle appearance.
11.Since our car is not a restoration, we opted for a set of Hella horns that were mounted near the stock location. The horns are small, lightweight and loud. We found them at Summit Racing.
12.Because early Corvettes have thick fiberglass, we found it hard to find grommets that would stay in place. We used short pieces of rubber hose through the fiberglass panel with a tie-wrap on either side to hold it in place. Wires are routed through the hose fully protected. After all wiring is complete a small dab of clear silicone seals the deal.
13.Because the dimmer switch mounts to the fiberglass floor we made this simple backing plate from a piece of stainless steel to reinforce the area.
14.When you are wiring a Corvette, grounds play a major role in electrical performance. The Ron Francis grounding (-) kit provides ample ground wires to perfectly ground everything on our C1.
15.We had welded small stainless steel plates into the chassis on all four corners, tapped for 1/4-20 bolts to act as grounding pads. We formed copper brackets from common tubing by flattening in a vise and drilling two holes.
16.A simple 90-degree bend completes the bracket. The copper bolt is part of the Ron Francis grounding kit. This copper bracket bolts to our chassis and the stud receives multiple ground wires for a perfect electrical connection.
17.Getting under a C1 dash to wire the gauges is a flexibility challenge. Once we got comfortable under there, wiring the SPW wipers and our temp and fuel gauges was very straightforward.
18.When it came time to wire the light switch we noticed the Ron Francis light switch came with a nice plug but did not have the Corvette knob. Swapping the knobs proved to be very simple.
19.After removing the set screw from the knob carefully clamp the shaft in a vise and gently tap the knob off the shaft.
20.Here we can see the difference in the shaft lengths. It is a simple swap; gently tap the Ron Francis shaft into the reproduction Corvette knob. The shaft was removed from the switch by pulling the switch out, pressing the release button and removing the shaft.
21.With the reproduction light switch labeled bezel and the Corvette knob in place we are ready to install the switch.
22.Using the light switch nut wrench it was simple to tighten the threaded insert that holds the switch in place. The end result is a factory appearance with a superior switch and wiring.
23.The Ron Francis harness plugs into the switch for a quick, safe and secure wiring connection. The long wires are there to allow for mounting the main panel in your chosen location.
24. We had our oversized tachometer custom built by Classic Instruments and they offer a “Halo-light” that illuminated a ring behind the gauge. We decided to use this option as a turn signal indicator since the small arrows in the dash are not that easy to see.
25.In order to have both turn signals from our ididit column illuminate a single indicator light we used a diode on each incoming turn signal indicator light. Think of this as a one-way valve that permits electrical flow only in one direction. This prevents unwanted power crossover through the single indicator light. It worked like a charm.
26.We spent several days wiring the car in an attempt to keep things neat and to ensure all wires were safely routed. We were very pleased when we tested our system and everything worked perfectly. Take your time, work carefully and read the instructions and you to can rewire a Corvette.
Optima Battery
Every car requires a battery and like many things in the automotive world there are legends, myths and downright incorrect information being circulated about this required and all-important piece of equipment. When we had a chance to talk with “Optima Jim” McIlvaine we asked him a few common questions.
Q:Why is a special charger recommended for AGM batteries and what does the AGM charge do differently. I ask this because, obviously, the automotive alternator does not know what type of battery is being charged.
A:It’s a common misconception that AGM batteries need special chargers, when that really isn’t the case. Most chargers will work just fine to charge AGM batteries under most circumstances. However, one of the benefits of AGM products is that their low internal resistance allows them to deliver current well beyond their specified ratings. That can be the difference between a car making it home safely or having to stop on the side of the road with a bad alternator.
The problem many battery chargers run into is when they are asked to recharge deeply discharged batteries. Many battery chargers have very basic circuitry that will either not deliver current to a battery that has been discharged below a minimum voltage level or may only deliver current for a brief amount of time and then shut off, if the battery hasn’t reached a minimum voltage level. The thought behind this limitation is any battery that has been discharged below about 10.5 volts, probably has lost a cell (~2.1V per cell) and cannot be recovered.
That may be true for a flooded battery, but as I mentioned before, AGM batteries can keep delivering current well beyond their rated specifications and as a result, end up at a voltage level well below 10.5 volts. In fact, it’s not uncommon for our sponsored tournament anglers to come off the water with their batteries discharged down into the 7-volt range on a windy day. The same thing can happen to a Corvette that sees infrequent use, especially if it is equipped with a car alarm and/or OnStar and sits in a garage where reception is poor.
Optima had asked charger manufacturers for years to integrate microprocessor technology into their chargers that can do a better job of analyzing and charging batteries and a few have, but many of the chargers commonly sold today are still using very antiquated technology.
Some other AGM battery manufacturers have responded to this widespread issue by making changes to their warranties that void coverage on deeply discharged batteries or batteries charged with unapproved chargers. Optima chose not to put such exclusions into our warranty, but we did take other steps to address this issue. We created a YouTube video, which explains how someone can recover a deeply discharged battery with a regular battery charger, by using a parallel charging technique. We also came out with our own line of battery chargers and maintainers that are microprocessor-controlled and can recover batteries that have been discharged down to 1.25 volts, which is best in the industry.
Q:Do you recommend always leaving a battery charger/tender on Optima batteries used in a typical collector car that is driven once a week or less?
A:I recommend always leaving a quality battery charger or maintainer on any battery in a typical collector car that doesn’t see regular use. I say “quality,” because there are many battery maintainers being sold in bargain bins at retailers that are not quality devices and may not properly regulate current going to a battery. If a charger specifically indicates it is microprocessor-controlled on its packaging, it is a much better option than one that doesn’t indicate much beyond a low price point. Of course, our Optima charger is designed to handle all batteries, including our AGM batteries.
I know folks have visited or at least watched videos of collections like the Ken Lingenfelter collection. I would encourage them to take another look and this time, look for battery maintainer cables coming out of his cars. It just makes sense to keep his collection well-maintained with battery chargers and maintainers. I’ll mention it again because it’s worth repeating, many of the newer cars in Ken’s collection are so packed with modern technology that their key-off load would completely discharge their batteries in a matter of weeks. Some of these cars even come equipped with battery maintainers to address this issue, but even with occasional use, the depth of discharge would give the alternator quite a workout for the brief amount of time it was in use and likely lead to premature failure.
Q:In the custom car world I have actually seen Optima batteries selected for the color coordination with the rest of the car. To the best of my knowledge the RedTop is best for automotive, any problem using a YellowTop or BlueTop battery?
A:RedTop batteries are designed and warrantied for starting applications, which covers the vast majority of automotive applications. However, some vehicles are equipped with accessories (large stereo systems, winches, etc.) that would make them deep-cycle applications, where the battery is likely to get deeply discharged. In those types of applications, we would recommend a YellowTop, which is designed and warrantied for both starting and deep-cycle use.
BlueTop batteries are the marine equivalent of our YellowTop batteries, except for the 34M, which is the marine equivalent of our Group 34 RedTop starting batteries. They are identical internally to their YellowTop and RedTop counterparts, but they do have auxiliary threaded terminals for use in marine and RV applications. There’s nothing wrong with using a specific color to coordinate with the rest of the car, as long as someone isn’t using a RedTop in a deep-cycle application, like a red Jeep with a winch.
Q:Does Optima make or recommend a specific type of battery disconnect switch, is it preferred to interrupt the ground or the positive terminal, or does it even matter?
A:Optima only manufactures batteries, chargers and maintainers, but there’re plenty of great companies making disconnect switches, sealed battery boxes, custom hold-downs and other battery accessories. It’s best to follow the manufacturer’s recommendations for their products. However, from personal experience, I can tell you that some battery disconnects are designed to only fit on one of the terminals.
If a disconnect doesn’t come with instructions, it should be easy to slip over the top of a terminal and tighten. Battery terminals are typically made from lead, which is a relatively soft metal that’s easy to damage. When we look at batteries that have been returned under warranty, many of them have damaged terminals. Some are top terminals that were bent or broken off because the battery cables were the only thing holding the battery in place. Others were side terminals that were over-tightened and stripped out or poorly connected, which sent all the current through one spot, generating so much heat that it melted the terminal out of the battery. Many racing sanctioning bodies also have specific rules for battery kill switches. Always review the rule book to ensure the switch is in compliance.
Photography by the Author