The original headlight ground circuit mod thread:
http://www.my-mc.com/messages/1/107511.htmlwritten by
Norm Keller.
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Headlight Ground Circuit Upgrade
The headlights are powered through the headlight relays and grounded through the (Green) common ground circuit wire. A voltage drop test of my 1994 ST1100A with 59 amp (rated 40 amp) alternator indicated that this circuit could stand improvement.
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Measuring the ground circuit voltage drop as follows:Headlight ground circuit voltage drop = 0.385 Volts @ alternator voltage 14.3 volts.
A rule of thumb for 12 volt circuits is that voltage drop should be less than 0.2 volts for any switch or wire.
For those who are not familiar with the concept of voltage drop, voltage drop in a wire or switch is undesirable. Voltage drop is an indicator that power is being consumed to overcome resistance, which should not be present. We gain nothing by heating wires or switches rather than using all available power to operate the headlights
In order to remove the voltage drop it is necessary to reduce the resistance in the ground circuit (wires leading to the battery /alternator negative. 14 gauge wires (green) were connected from the headlight ground spade connectors in the headlight plugs. The two new (additional) ground wires were connected to a 10/12 gauge ¼†(6mm) connector which is bolted to ground (the frame) at the fairing brace in the front of the steering head.
Photo:
Voltage Drop 1:
In order to connect the voltmeter, a headlight plug was pulled out and a voltmeter + probe pushed into the
space between the ground terminal and the plug body.
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%201.jpg)
Photo:
Voltage Drop 2:
The voltmeter was grounded to a PAIR stud because it was handy.
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%202.jpg)
Following the installation, the ground circuit voltage drop was measured at 0.029 volts!
For interest, the H4 bulbs are Sylvania Silver Star 50/65 Watt bulbs at alternator voltage 14.3 volts current flow through each bulb is as follows: Low beam = 4.6 amps. High beam = 5.2 amps.
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Steps involved in this modification are as follows:Photo #1: Pull the headlight plugs from the back of each bulb. This view looks through the space between the fairing and the fork tubes. My hand can be seen reaching to unplug the right hand plug.
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%203.jpg)
Photo #2: Reach up from under the front wheel to remove the plugs. The complete procedure can easily be performed through this access without any other disassembly. It may be desirable to place a soft cover over the front fender to prevent scratches or burns.
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%204.jpg)
Photo #3: Note the green ground wire located in the left side (installed position) of the headlight plug. It will be necessary to remove the wire and terminal from the body of the plug to allow the additional ground wire to be soldered to the ground connector. I prefer to avoid cutting original wires or modifying components so that they cannot be returned to stock. This is just one of my quirks. (VBG)
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%205.jpg)
Photo #4: Fairing support bolt can be used as the attachment point for the new ground wires. Note that I have already mounted a cigarette lighter socket here to power my GPS. The GPS has a power converter in the form of the cigarette lighter plug and it seems simpler to retain the plug assembly as the GPS is sometimes used in other vehicles.
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%206.jpg)
Photo #5: Removing the bolt. Note that I used a hole in the bracket to attach the ground connector so did not have to remove the bolt.
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%207.jpg)
Photo #6: The ground wire and terminal removed from the plug body.
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%208.jpg)
Photo #7: I hope that you can see the small tang, which stands out from the upper side of the terminal. This tang acts as a barb to retain the terminal in the body of the connector. This removal activity is an ideal first time project for learning to deal with terminals because the tang can be seen when looking into the space between the terminal “boxes†in the plug body. Look into the center to the body from the side away from the wires. The terminal needs be pushed farther into the connector body to move the end of the tang free of the body. Use a small tool such as the terminal removal tool in my hand to bend the tang back in line with the connector so that the tang will not bear against the body as the wire and terminal are withdrawn.
When the terminal is out of the body, use a small tool to bend the tang outward again to allow it to act as a barb to retain the terminal when reinstalled. The tang needs only be bend outward sufficiently to catch the ledge in the body after the terminal is pushed into position.
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%209.jpg)
Photo #8: An alligator clip is used to hold the new wire against the top edge of the terminal during soldering. Allowing a solder joint to flex before the solder cools will fracture the solder and produce a weak joint. Refer to the other two wire terminals, which are still in the headlight plug. You will notice that the new wire must be attached across the top of the terminal so that it does not prevent the terminal from being pushed into place. Note that the solder joint is not shown clearly in the photo. I actually solder very well. (VBG)
(http://www.st-riders.net/aow/AOW%20-%20ST1100/Headlight%20Ground%20Circuit%20Upgrade%20-%20ST1100/Pic%2010.jpg)
Sorry about the quality of the photos. I was on my own and they looked OK on the camera viewer.
This is my first try at posting an article with photos. Even more work to resize and such than to write the procedure. Doing it took ½ hour but the article and post ……
HIH
Norm