So, you have your classic muscle car totally restored, huh? Perfectly flawless bodywork, covered by a paint job so magnificent that Michelangelo would be envious. An engine compartment so exactingly correct that you can recite, on demand, every phosphate, bare metal, cadmium or slop gray coating used on each and every clip, nut, bolt or fastener. The engine, of course, is so clean that you could eat off of it. Except you would never let something that filthy touch it. The interior is spotless. You keep the interior so clean that it borders on hospital sanitary. All this makes for a perfect example of Detroit’s Finest in the same (or better!) operating condition that was enjoyed by the original owner on the day he took delivery. So after a long day of local car-show duty, you take down all your display material, load up all the cleaners and polishing towels, put away the folding chairs and cold-drink coolers, and if you were lucky enough to get one, so carefully that it won’t get damaged, pack up your 1st Place trophy. Or as my wife calls them…dust collectors. In fact, everything is just about perfect with your pride and joy. That is until you get out on the road and turn on the headlights and discover that you can’t see very well. And if you are one of the real lucky ones, you may even have one of those cars that have the famous blinking headlight syndrome. It seems that no matter what you do, the headlights on your car just don’t seem to be very bright. Maybe you’ve upgraded them to the newer halogen-type sealed beam lamps, but they don’t seem to throw any more light than the regular old sealed beams do. Why is this? Are we classic car aficionados forever doomed to drive around in vehicles with lighting so poor that it is indeed dangerous to be out after dusk? The answer to that is a resounding ‘No’!





SO WHAT IS THE PROBLEM?

The problem with the headlights on our street-machines is in the design and construction of the electrical wiring used for the headlights. The factory originally used the thinnest and cheapest wire that they could get away with when the wiring harness’s were made for our cars. These thin-wire harness’s were barely adequate when the vehicles were new. With 20-30+ years of age, heat, oil, solvents and dirt, and bad grounds to contend with, it is a wonder that some of them continue to work at all. Add to that the fact that the actual design of the wiring harness used the most simplistic method possible to send power to the headlights.

PROBLEM #1: THE POOR POWER PATH

I call the route that the electricity must follow to light up your headlights the ‘power path’. In a factory-designed wiring harness, the power path starts at the power source, neither the battery, the starter solenoid, the ‘B+’ connection on the back of the alternator, or some other location that gets direct juice from the battery and alternator. From this source, the power travels all the way up to and thru the firewall, to the dashboard and into the headlight switch. From the headlight switch, the power then travels thru the dimmer switch, or on some newer vehicles, the multi-function switch. From the dimmer switch, the power then travels back thru the firewall, and all the way back to the headlights. Since the headlights are grounded to the car’s chassis, the power flows into the headlights, illuminating them, and out to the common vehicle ground, and back to the power source, which also uses the same common ground. This is a very long and torturous path the power must travel, and it does this with wiring that is very thin, usually 18-gauge. On rare occasions you may find a car that used 16-gauge from the factory. This is far too thin and lightweight for wire that must be used for such an incredible amount of power that needs to find its way to the headlights. The too-thin wire has a tendency to heat up from all this power passing thru it, and causes resistance in the wiring. Resistance has the effect of partially blocking the flow of electricity, reducing the amount of voltage that ultimately gets to your headlights. This, of course, makes your headlights a lot less bright than they should be. The resistance also has the tendency of causing the wiring to heat up even more, setting up even more resistance, further reducing the voltage to the headlights!

HOW MUCH VOLTAGE DROP?

Full voltage, coming off the battery/alternator is around 13.5 volts. At this voltage, your headlights will illuminate at 100% of their rated capacity. Unfortunately, most factory headlight wiring never supplies this amount of voltage to the headlights. It is common for most headlights to receive around 11.5 volts, or about 85% of the full voltage available. According to ‘Hella’, at 85% voltage a typical headlight will put out 53% of its rated illumination. At 75% voltage, that same headlight will only put out 45% of its capacity! This commonly causes headlights to have a yellowish or even brownish tint to them. Old, degraded inefficient wiring with bad grounds commonly supply 75% and lower voltage to our headlights! And speaking of grounds…

YOU GOTTA’ STAY GROUNDED!

All automobiles use what is known as a common ground. This means that most every electrical accessory on the vehicle is grounded to the vehicle’s chassis, and the chassis is grounded thru the battery to the engine block. This is convenient for the manufacturer, because everything can be grounded with a short run of wire at just about anywhere on the vehicle. Plus, it saves on running long lengths of wire back to the accessory. The problem is that a common ground system does not produce the best uniform grounding available at all times, and the effects of age, dirt and corrosion at the ground connection often all lead to a poor pathway for the power to follow. Suffice it to say, proper grounds are a necessity!

RESISTANCE= HEAT!

With all of this resistance in the system, the headlight switch and dimmer switch will get very hot also! In fact, if the headlight switch gets hot enough, the internal ‘thermal breaker’ will trip, cutting off all power to the headlights until it has cooled down enough to resume operating. Some headlight switches can get so fatigued from this constant excessive operating temperature that it causes the headlights to flash on and off sporadically. Eventually, the switch will completely fail. In the worst case scenario, the overheated wiring and switches can even lead to a vehicle fire! That’s no good!

WHAT ABOUT HIGH OUTPUT LIGHTS?

The use of high output lights will only put more demand on the sub-standard wiring, causing more heat and resistance. Result? Your expensive high-output headlights are no brighter than the standard ones! Remember, the problem isn’t necessarily that the headlights can’t produce enough illumination. The problem is that the headlights aren’t getting enough voltage to produce enough illumination! So what do we do about this?

THE ANSWER?...RELAYS!

A relay is simply a low-voltage switch that is used to activate a separate high-power circuit. The relay allows you to turn on this high-power circuit from a remote location. The high-power circuit we are talking about is the headlight circuit, which will be totally located under the hood, as close to the battery and headlights as possible. The short path for the wiring allows full-voltage to the headlights. Now, to turn on this high-power circuit, we could not easily open the hood and flip a switch to turn on the headlights, so we need a remote method of activating the headlight circuit. The relay is the remote switch, and it is triggered by your vehicle’s existing headlamp wiring, originally used to carry the full load of the headlamp voltage. Instead of the 11 to 13 amps that normally pass thru this wiring, the relay only needs a fraction of this to operate, something in the area of 20-30 mA (milliamps). The factory wiring harness from the engine compartment to the dashboard is more than adequate for this. The relays that we will use for this installation are the ‘Bosch’ style relays. They are about 1” square, and are extremely reliable. The connections on the relays, originally decided on by Bosch, but now practically universal, are labeled as follows:

• 86 switching (relay) input 
• 85 switching (relay) output
• 30 high-power circuit input 
• 87 high-power circuit output

The type of relays to use in this installation have two #87 connections, allowing you to easily hook up two leads to the #87 terminals. For our purposes, this will come in handy. Make sure to use a quality relay that is rated to handle 40 amps.

For a standard system, we will use two separate relays, one for the high beams and one for the low beams. The real beauty of this whole thing is that we can install a far superior relay system very easily, in only a few minutes, and with very little modification the factory wiring. Now there are complete, aftermarket wiring harnesses available that are designed for just this purpose, but without fail they all use sub-standard connectors and still too-thin wiring. To make matters worse, most of them use proprietary, hard to find fuses that are not available in a typical auto parts store, and the relays are sourced from a cheap, nameless overseas manufacturer. Since the whole idea here is to upgrade your headlamp wiring to its maximum potential, it’s makes absolutely no sense to modify the existing factory-installed wiring with some other wiring that is prone to the same type of problems. The only real solution is to use the highest-grade components available, and to assemble the harness yourself using high-quality wire. This will ensure that you are indeed making the maximum improvement to your headlamp system, plus the finished product will be custom-fit to your particular vehicle.

These high-quality relay and wiring components are available from Daniel Stern Lighting Consultancy, a leader in the field of automotive lighting. Mr. Stern has consulted for the U.S. and Canadian governments in regards to automotive lighting concerns.

CREATING THE NEW CIRCUITS

Think of the factory circuit as a loop. The loop goes from the battery, to the headlight switch, the dimmer switch, to the headlights and back to the battery. This loop forms both the power path and the switching path. All available voltage travels thru the entire circuit. We are going to simply run a new and separate, high-capacity power path, while the existing wiring will be used only as the totally separate switching path.

CREATING THE NEW POWER PATH

To create the new power path, we need to use some wire that is up to the job of carrying this much voltage. The 18 or 16 gauge wiring used in the factory harness is simply way too thin for this purpose. In this circumstance, bigger is definitely better. 14 gauge wire would be a big improvement, but 12 gauge wire is preferable. You can even use 10 gauge wiring for the entire power path if you want to, but for a stock headlamp system, that is usually a little over-kill. A combination of 12 gauge and 10 gauge wiring is what I recommend, but not just any wire will do. No, you must use the highest quality automotive grade wire you can find. And it must be of the stranded type. Never use the solid core household type of wiring! So get yourself several feet of 10 and 12 gauge wire, in red, black and green. Do not make the rookie mistake of wiring the new circuit in all one-color wiring. It is very difficult to keep the circuit straight as you are wiring it, and next to impossible to diagnose if problems arise down the road!

LET’S GRAB SOME POWER!

You will want to take the power off the positive post of the battery, or if possible, where the positive battery cable connects to the starter solenoid. Alternately, you can pull the power off the ‘B+’ terminal on the back of the alternator. Run a 10 gauge wire (red) of no more than 5 inches from the power source to a nice, heavy duty 30-amp in-line fuse holder. Make sure and use heavy-duty ring-lugs for the connections, and heat-shrink them for superior weather resistance. From the fuse-holder, run a 10-gauge wire (red) to relay #1 (low beams). You will want to make this wire as short as possible, so mount the relay as close to the fuse-holder as you can. Hook this wire up to the terminal on the #1 relay marked ‘30’ (power input). As before, use good-quality connectors, and heat-shrink to protect from weather. Now, hook another 10 gauge wire (red) to one of the two terminals on the #1 relay marked ‘87’. The other end of this wire should be long enough to reach the headlamp farthest from the relay. On the back of your new headlamp socket, the labeling is as follows:

• 56a high-beam feed 
• 56b low- beam feed 
• 31 ground

Unhook the original socket from each headlamp and just let them hang loose for now: we ’ll get to them in a while. Take the long wire from the relay to the headlamp and hook it up to the connector on the back of the headlamp marked ‘56b’. Hook another 12 gauge wire (red) from the second # ‘87’ terminal on relay #1 to the ‘56b’ connection on the opposite headlight.

On each headlight, hook a length of 10 gauge wire (black) to the connection marked ‘31’, and run the other end back to a good, clean ground, such as the alternator housing, the engine block, engine accessory bracket or the battery negative terminal. Do not ground this wire to the body! A good ground is crucial so you can get the best performance from the upgrade.

OK. WHAT EXACTLY DID WE DO?

You have completed the new power path for the low beams to each headlight! Now we need to do the same for the high-beams:

Install the second fuse-holder and relay as listed above, and wire them the same, with the following exceptions: the wires running to the headlamps will be the GREEN 12 gauge wire instead of the red wire. These green wires will hook up to the headlight sockets on the connection labeled ‘56a’, the high-beam feed. If your vehicle has separate bulbs for high and low beams, just hook the wires to the appropriate bulbs. The low-beam bulbs have three terminals (high-beam power, low-beam power and ground), while the high-beam bulbs have only two connections.( power and ground) You will have to ground each as recommended above. It’s worth mentioning again: MAKE SURE that all your splices and connections are solid, and heat-shrink them to ensure against weather related corrosion and degradation.

There you go! You have completed the new, high capacity power path to your headlights!

CREATING THE SWITCHING PATH

You now have a new power path to both headlamps, but both of your headlamp connectors are dangling loose, right? Great! We are going to use them to operate the switching of the high beam relay and the low beam relay. If you use the proper connectors, you won’t even have to cut any of your existing wiring either! On the headlight socket that is closest to the relays, find the connection inside that corresponds to the ‘56a’ (high beam) connector on the back of the headlamps. Hook a 12 gauge wire (green) to this ‘56a’ connector and run it to the #2 relay (high-beam). Connect the other end of this wire to the terminal marked ‘86’ (switching input) on the #2 relay. On this same headlight socket, find the connection that corresponds to the ‘31’ (ground) connector on the back of the headlamps. Run a 12 gauge (black) wire from this ‘31’ connection to the terminal marked ‘85’ (switching output). For the remaining connector inside the headlight connector, heat-shrink a connector with no wire in it, and install it on the unused connector. This will prevent any short-circuiting and corrosion.

What we now have is one of the headlight connectors powering the relay for the high-beams, and a loose connector on the other side of the vehicle. The loose connector will now be hooked up to power the low-beam relay.

On the loose connector, find the connection that corresponds to the connector on the back of the headlight labeled as ‘56b’ (low-beam). Run a 12 gauge (red) wire from this connector to relay #1 (low beam), and hook it up to the terminal marked ‘86’ (switching input). Then run a second 12 gauge (black) wire from the # ‘31’ terminal in the headlight connector to relay #1 (low beam). Cap off the third un-used connector as before, and you're done!

OK, SO WHAT DO WE HAVE?

We have made a new, high-capacity power path for the headlamps, and our existing wiring is now used as only a switching path. One headlight connector turns on the high beams, the other turns on the low beams.

At this point, make sure that all of your connections are well insulated from moisture, and neatly tie-up and attach the wires you have run. A nice, durable wiring loom (wire cover) is available from any auto-parts store, and gives a professional look to the job. Remember, your installation is only as good as the quality of your work. So turn on your lights and enjoy the nice, white and full-brightness that they should have had in the first place!

At this point your vehicle’s lights will be getting the full voltage they were designed to get in the first place. However, the issue of what type of bulbs to use is still in question. If your car uses the old-style sealed beam headlamps, don’t despair! You are not totally handcuffed to old technology. The original-equipment style sealed beams that came on your car from ‘back in the day’ just don’t have the capability of performing as well as some of the newer, more expensive lighting systems used on modern vehicles.

All is not lost, however: there are much higher-performance replaceable-bulb headlamps available from makers like Bosch, Marchal and Cibie. These component-style assemblies replace the older round and rectangular sealed-beam design headlamps that came as original equipment. With just a little effort on your part, they are not too difficult to find. They are more expensive than the poor-performing standard issue bulbs, but like the finer things in life…once you get used to high-quality, you’ll never go back!

When looking for higher-quality bulbs, steer clear from anything that advertises things like “100 watts of light from a 55 watt bulb”. Light output is measured in lumens, not watts. A watt is a measure of power, and if you have 55 watts going in, then you can only have 55 watts coming out. Another fad that has become popular is the blue tinted replacement bulbs. These are intended to give your vehicle that modern H.I.D. (high intensity discharge) look, but it is all for show, and at the expense of usable light output. They use tinted glass on the bulb cover, which reduces the total amount of light output. Exactly the opposite of what you want a headlight to do! Without fail, when the blue-tinted Extra-White headlight bulbs are tested they produce considerably lower output than their counterparts with clear glass.

With your new, upgraded relay set-up in place, a high-quality, high-output bulb will far outperform the typical OEM-style junk that is sold in most auto parts and discount stores.




Kit Sullivan is a 15+ year automotive lubrication engineer and a classic and muscle car enthusiast and collector