The headlights of an old or out-of-print car are dark! In such a case, let's suspect wiring deterioration and review the ground wiring!

As LED bulbs for headlights become more popular, more and more users are installing them in old and out-of-print vehicles. On the other hand, there are many riders who prefer the glow of old-fashioned filaments, even if they are a bit dark, to the luminous color of digital LEDs. Some riders seem to have given up on the idea that it is inevitable that the headlights on older bikes are dim, but there is a possibility of increasing the light intensity simply by reviewing the wiring that has deteriorated over time. Here we introduce a technique to brighten the headlight without using LED bulbs or a buffer relay.

From the battery to the light bulbs, the wiring of old cars is full of resistance elements

In a 12V car, the battery terminal voltage in a fully charged state is close to 12.8V, but the voltage drops slightly with each switch and terminal, and can lose nearly 1V at the connector part leading to the headlight bulb. Even if the resistance measured at both male and female ends of a male and female connector terminal is 0 Ω, the more contacts there are, the more the slightest resistance builds up, contributing to the final voltage drop. When inspecting the wiring of old and out-of-print cars, the coverings on the terminals are often deteriorated as if burnt, which is evidence that the current flowing through them has been wasted as heat, causing a reduction in the amount of light emitted by the headlights. In addition to the metal connector terminals, the contacts of the headlight switch and the dimmer switch that switches between high and low are also subject to oxidation and wear due to age-related deterioration, resulting in loss of power even when current is flowing, leading to voltage drops. One of the most effective countermeasures against such metal fatigue is to incorporate a battery-direct relay, or so-called "back-to-back relay," in which new wiring is laid from the battery to the headlight bulbs. The existing wiring is used as the switch power supply to activate the relay, and the current actually flowing to the headlights is a new dedicated line, eliminating intermediate losses.

Check the terminals of the connectors leading to the headlight bulb terminals!

If the headlights are dark, the situation will certainly be improved by incorporating a buff relay, no questions asked. On the other hand, checking the existing wiring can also provide clues for improvement. The Kawasaki Z1R shown here has been owned by multiple owners who have replaced each other, and it has been through many iterations, which is common for out-of-print vehicles. In the process, an external harness was installed, but the owner was dissatisfied that the headlights were not bright enough. In older cars, there is a possibility that the performance of the headlight itself or the bulb has deteriorated due to fogging of the reflector or dirt on the inside of the lens, but in the case of this bike, there was a problem with the negative terminal of the connector that connects to the H4 bulb. Whenever you insert or remove the light connector, it is essential to hold the connector itself, but depending on the situation, you may also hold the wiring at the connector and pull it. In such cases, some external harnesses have poorly caulked terminals, and the core wires may come loose. It is easy to tell if the wire is completely disconnected, but if the core wire is broken or disconnected halfway through, which is not enough to turn off the headlights, you may not notice a problem. This is true not only for broken wires, but also for corrosion and rust on the core wire. It is not uncommon for an out-of-print car to show green oxidation (verdigris) on the caulking area and core wire when the terminal is pulled out from the connector. In the case of external harnesses, in addition to the caulking, the quality of the terminals themselves also requires attention. Whether it is a connector or a flat terminal, subtle differences in thickness or thickness can lead to poor contact. When replacing a harness, replace not only the main harness but also the sub-harness at the same time, and also pay attention to the condition of the terminals inserted inside the connector.

Simply changing the negative wire of the headlight connector back to the body and battery will make a difference.

I digress, but in repairing the headlight connector, which had a problem with the caulking of the minus terminal, I grounded the newly fabricated wiring to the crankcase of the engine instead of returning it to the main harness. In the existing wiring, the minus wire of the headlight is connected to the main harness and merges with the minus of the electrical components in various parts of the car body and is grounded to the car body. In this case, as with the positive side, the more contacts there are due to the merging and shunting of wires, the more contact resistance is likely to increase. Therefore, we tried to create a kind of earthing effect by wiring directly from the negative terminal of the headlight connector to the crankcase. The same effect can be expected by connecting to the negative terminal of the battery instead of the crankcase. There are various opinions about arcing, but there is no doubt that not only the "outward" route from the battery to the electrical components, but also the "return" route from the electrical components back to the car body and battery is important when considering the entire circuit. In this case, the main cause of the headlight dimness was a faulty break in the wiring at the terminal. Even if there is no caulking problem, connecting the negative wire to the car body or battery can remove the negative element, even if the effect is not dramatic. It is also effective not only for headlights, but also for other electrical components such as turn signals and horns that are wired only to the positive side and the negative side to the body ground. Adding negative wiring is less expensive than installing a new relay or fuse, and there is no need to think about the space required to install these components. This analog solution is not relevant to older cars with less deteriorated wiring or LED headlight models that consume less power, but it is good to know that this method is also effective for older cars and out-of-print cars. [/caption

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