A Little Illumination on Lighting

August 13, 2010 | By: Scott Holton

One of the more popular modifications that people like to perform on their scoot is changing the lighting. Some folks want more light in order to see better at night. But what some would-be electricians don’t realize is that installing higher than standard (55-60) wattage H4 bulbs in their halogen headlight increases the amount of current running through the stock wiring.

A standard 55-watt low-beam bulb will draw 3.5 to 4.5 amps. A 60-watt high beam draws 4.2 to 5 amps. Some of the more common higher wattage bulbs available these days are 55-100, 80-100 and 100-130.

Current draws for each will be:

55/100 W = 3.5 to 4.5 & 7.5 to 8.3 amps

80/100 W = 6 to 6.66 & 7.5 to 8.3 amps

100/130 W= 7.5 to 8.3 & 9.5 to 10.8 amps

Because of the increased amperage these bulbs require, the wiring and headlamp plug are at risk. That’s because the stock wiring is too small to handle these current levels. What you end up with is burnt wires and melted connections. So if it’s really your intention to install one of these brighter bulbs, an upgrade in the gauge of the wire to the headlamp is highly recommended.

Another thing to consider with these super bright bulbs is the effect they can have on the bike’s charging system. Shovels (from 1970 to ’84) come with 15-, 17- and 22-amp alternators, and early Evo Big Twins (1984 to ’88) have 22-amp alternators. Sportsters (1967 to ’79) have 10-amp charging, while ’80 to early ’84 bikes have 13 amps, late ’84 to ’90 feature 19 amps and 1991 to 2005 bikes have 22-amp systems. Upgrading to the higher wattage bulb is impossible on the smaller amp charging systems. To upgrade, the 22-amp system would be the lowest amp output recommended. There just isn’t enough current output to run everything required and keep the battery charged. Those Big Twins from 1989 and later have a healthy 32-amp alternator, so this is not a challenge.

Although there are several high-intensity H4 upgrades available, a good option is the PIAA H4 headlight bulb (J&P Part No. 380-889).  It’s rated 60/55w with the light output of 110/100w lamp. This produces a bright cool light at 4000K.  If the bike has spotlights on it, the H3 PIAA bulb is a good choice (J&P Part No. 381-403). The big advantage to these bulbs is that while they put out about twice the light as a standard H3/H4 bulb, they don’t require any more electricity to run than the OEM  bulb on most bikes.

Another popular lighting modification is replacing the turn signals with a smaller, sleeker model. Not affected by vibration, an LED (light emitting diode) style light is often chosen due to its bright, vibrant light and incredible durability.  In applications that have a self-canceling turn signal, a load equalizer is required. Since the LED light changes the resistance in the circuit, the difference in current draw will confuse the original processor into thinking that the bulb is burned out. This can cause a no-flash or double-flash condition.

A load equalizer, such as a Badlands Turn Signal Equalizer II (J&P Part No. 320-184), will correct this condition by fooling the processor into thinking the stock bulb is still in the circuit. Your new LED turn signal will flash and cancel normally. These units are easily installed by tying into either the front- or rear-turn signal circuit.  First, locate the correct wires in your service manual’s wiring diagram. Verify the correct wires by using a test light in the turn signal wires.  Turn on the ignition and press the turn signal button.  Test each side. The tester will light up if you have the right wire.  Make sure you don’t tie into the running light wire.  Once you’ve verified the correct signal wires, connect the wires from the load equalizer to the left- and right-turn signals.  Place the load equalizer unit away from any wiring looms or soft plastics to avoid any heat generated during normal operation.

A load equalizer is also required if a small, marker light-type light is used as a four-way flasher. Due to possible heat buildup in the unit over a longer period of time, it’s a good idea to restrict usage. A reminder: While these small, marker light-type lights look good on a show bike, they should not be used on the street, because they can’t be seen as readily as a DOT-approved light — especially in the daytime.

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