Must Have Harley Engine Tips and Tricks

Must Have Harley Engine Tips and TricksThe Oil Pressure and Neutral lights on your dash panel may be a potential source of disaster. In aftermarket and most factory models these indicator lights are nothing but 12 volt bulbs mounted in twist-lock receptacles. Unfortunately, the design of the receptacles leads to a high potential for short circuits. A small piece of conductive debris (like a metal shaving) can lodge itself between the inner shell and the dash, causing the light to turn on in error. If the light is intended to indicate that the bike is in neutral you may end up trying to start it in gear. Or, as has happened to me, your oil-pressure light may come on when there is no loss of pressure!

Fortunately, there is a very simple remedy for the poor design of these light bulb sockets. You can use 12 volt HIGH INTENSITY LED’s to replace the bulbs and sockets.

A stock socket consists of a shell with a keyway for the tiny posts on the bulb, and a center conductor at the base that makes contact with the center conductor on the bulb. The shell is supposed to be insulated from the dash by a fiber washer. In theory, the shell should never make direct contact with ground. In practice, the shell can easily be bent or contaminated with debris and ground itself. The wiring of the bulbs is with +12 volts to the center conductor on the bulb, and the ground side made or broken to provide the indicated signal. Any light that can handle 12 volts and has its ungrounded side connected to +12 permanently, and its grounded side connected to an oil pressure or neutral switch will do what the stock assembly does!

So, go to Radio Shack or your local electronic parts supply house and buy two 12-volt automotive quality HIGH INTENSITY LEDs. If you can find a mounting kit for the LEDs make sure it fits into the holes where the light bulb sockets were installed in your dash. If you can’t find a mounting kit, it is possible to use grommets.

WIRING: As with all solid state devices, you must be careful to limit the current that can go through the LED. Look in the specs for the LEDs you are using and find the maximum current allowed by the devices. You can then use OHM’s Law to derive the necessary resistance to put in series with the LED. In case you don’t remember, Ohm’s Law is expressed as E=I*R, or “Voltage is equal to Current times Resistance.” You can find the resistance by simple algebraic substitution: R=E/I, or “Resistance is equal to Voltage divided by Current.” Voltage is in Volts, current is in Amperes and resistance is in Ohms.

Example: For a current of 60 milliamps (ma) and a voltage of 12 volts the required resistance will be E(12)/I(.06) or 200 Ohms.

If the LED you choose is designed to be used in instrumentation it may not need to have an external current-limiting resistor. Read the instructions that come with the LED carefully.

Unless your LED panel light assembly has a built-in resistor, you need to place a suitable resistor IN SERIES with the LED, between the +12 volt source and the LED. IMPORTANT: If you don’t use a resistor of the proper value the LED will quickly burn out. If you DO wire it correctly, the LED will last longer than the bike, (or longer than YOU for that matter), and it won’t be affected by vibration.

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  1. Rob Fleming - August 30, 2011

    New blog post: Must Have Harley Engine Tips and Tricks

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