Article [13] ST1300 - Headlight Wiring Diagram

2005RedRider

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Re: ST1300 headlight wiring diagram

I wonder if it would be helpful to create a voltage drop of approximately .4VDC at Fuse "G" (from the MileHigh's wiring diagram)? Wouldn't this equalize the voltage between the right and left headlight?

A small resistor maybe? :rolleyes:

Resistance equals voltage squared, divided by power. So, for a 45 watt bulb, using the average voltage of the right headlight of 13.9 VDC, the resistor would have to be about 4.3 ohms. Right?

Dale :)
 
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MileHigh

MileHigh

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Re: ST1300 headlight wiring diagram

An update to headlamp wiring 4-26-09

The Honda service manual wiring diagram, for the ST1300 (non P model,) is wrong!

The relay names are reversed and, the lamp filaments are reversed.

Honda uses blue wires for HI beam and white wires for LO beam.

The outer filaments, in the bulbs, are LO beam. The inner filaments are HI beam.

The left lamp uses relays for power. The right lamp uses the dimmer switch for power.

The relays are under the left side cover. The LO relay is towards the front and, the HI relay is towards the back. Only the left headlight uses the relays.

The relays have rubber dust covers with a slot in the back. The slot slides over a metal tab to hold the relay in position.

Right and left are sitting on the bike looking forward.



The diagram below shows the correct relay names & lamp filament placement.

8123.jpg
Included are some other pictures of the ST1300 (non P model) headlamp system.



8126.jpg
8129.jpg
This is the left connector, flipped backwards, looking in at the bulb connections.

8130.jpg

8128.jpg

8127.jpg

8125.jpg

8124.jpg
Hope this helps.
 
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CruisingDog

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Re: ST1300 headlight wiring diagram

Mark (MileHigh), thanks for creating the diagram. I made some measurements while changing my left-hand bulb last week and I was going to create a similar diagram. It would not have looked anywhere near as good as yours.

Being on the forum for a number of years now I always took it with a grain of salt whenever I would run across a comment from someone saying that their left hand light burned out. I naturally assumed that both bulbs would have been basically wired the same and that it was sheer coincidence that more left hand bulbs were being replaced than right side ones.

But after losing an Osram Silverstar bulb on the left hand side after only installing it seven months prior, I began to wonder if there really was some truth to the grumblings.

After getting my hands on a readable copy of the wiring diagram I could indeed see that there was a distinct difference in the manner in which both bulbs were powered. Which is what you can see in Mark's diagram. Essentially the left hand bulb gets its power directly from the battery via the contacts of two relays (one for low beam, one for high). The right hand bulb receives its power from a different battery circuit that doesn't utilize any relays but passes through various switches (ignition, starter and headlight). In a perfect world it wouldn't make any difference, after all a relay is simply another form of a switch but in the real world there are IR losses (voltage drops) across all switches that need to be taken into account. In the ST's case this results in more losses in the right hand circuit versus the left.

I took the time to make some voltage measurements at the headlight connector of each bulb. The first set of measurements used the ground terminal of the respective headlight bulb as the negative input for the multimeter and the second set used the negative terminal of the battery as the negative input of the multimeter.

  • Left - low beam > 14.33V (gnd @ bulb)
  • Left - high beam > 14.31V (gnd @ bulb)
  • Left - low beam > 14.29V (gnd @ battery)
  • Left - high beam > 14.30V (gnd @ battery)
  • Right - low beam > 13.85V (gnd @ bulb)
  • Right - high beam > 13.87V (gnd @ bulb)
  • Right - low beam > 13.90V (gnd @ battery)
  • Right - high beam > 13.94V (gnd @ battery)

If you average out the difference in voltage between the bulbs for each condition listed above you get 0.4175V (0.48, 0.44, 0.39, & 0.36).

Most people might think that 0.4V doesn't sound like much BUT for an incandescent light bulb (which is what these are even though their called halogen lamps) that difference has a HUGE IMPACT on the life of a bulb!!!

The relationship between the life factor of a light bulb to its design voltage varies by a factor of 12! For an illustration of this refer to the two charts located at the bottom of this link.

As an example using the low beam operating at 14.31V (ignoring other loads on the electrical system that might bring this voltage down) and the bulb is rated at 13.2V, the bulb is being operated at 1.08 factor of its design which corresponds to an operating life 0.4 times its rated value. If the bulb had a low filament rating of 800 hours, operating it at the higher level reduces its theoretical life to 320 hours.

You might be surprised to discover that many of the available aftermarket bulbs that you can put in your ST (9003, H4 types), the rated life of the high beam element is half of the low beam. So if you generally travel during the day with your high beams on you will find that you are replacing these more often. [Note: I could not located any technical specs for the actual bulb that Honda uses in the ST... both elements might be rated for the same length]

I'd be willing to bet that most owners who place auxiliary lighting on their bike wire the lights similar to how the left hand bulb is wired, that is, running the power from the battery through a set of relay contacts. If the right hand side bulb was wired identically I guess that there never would have been anything to talk about because the bulbs would blow on average at the same rate. So the next time you lose your left hand headlight... thank Honda for increasing the reliability of the right hand side bulbs! ;)
So I guess the answer is to put a small series resistor with the bulb to drop some of the voltage.

65W bulb @ 14.4V = 4.51A,

To drop 1V, R = 1V / 4.51A = 0.22 Ohms. Power rating for the resistor = I^2 * R = 0.22 * 20.375 or V^2/R = 1^2/ (1/4.51) = 4.51W

So a series resistor of .25 Ohms and a rating of 10W would work. It'll get warm though!
 

Blue STreak

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Re: ST1300 headlight wiring diagram

Just wanted to thank Mark for this wiring diagram. I've been blowing a headlight fuse, only on low beam, and think I've got it solved. But without this diagram, it would have taken me much, much longer to track it down.
 
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Re: ST1300 headlight wiring diagram

FWIW: I use the Blue/White wire that travels from the start switch on the throttle side switch housing to the High/Low Beam selector switch on the clutch housing as the voltage source for two sets of relays. One Relay serves as the power source for my Aux Lights, the other relay is what powers my supplimental electronics power bus. This allows for the load of the Aux lights and the radio, intercom, grips, amplifier, GPS and security alarm to be un powered when the starter is engaged. This provides more juice for starting the bike, and protects the electronics from the Inductive flyback off of the starter motor that can damage these more sensitive devices.
 
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Re: ST1300 headlight wiring diagram

FWIW: I use the Blue/White wire that travels from the start switch on the throttle side switch housing to the High/Low Beam selector switch on the clutch housing as the voltage source for two sets of relays. One Relay serves as the power source for my Aux Lights, the other relay is what powers my supplimental electronics power bus. This allows for the load of the Aux lights and the radio, intercom, grips, amplifier, GPS and security alarm to be un powered when the starter is engaged. This provides more juice for starting the bike, and protects the electronics from the Inductive flyback off of the starter motor that can damage these more sensitive devices.
Oh, I like this idea.

On another note, has anyone else removed the power load thru the ignition switch by using the red/black wire as a relay trigger source and instead of directly as system power? Takes some fiddling on the back of the main fuse block. I did it on ReSTored with an added 40 amp relay. Down side, that's the relay that failed on me at Sink's last October. Maybe it ain't worth bothering with?

Comments appreciated.

Mark, your new diagrams are great. I never realized those relays only operate one light.
 

Papa

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Re: ST1300-Headlight Wiring Diagram

where else could one find such gems of info? thanks
 
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This was a big help! Thank You for this write up.. I had a problem with the left low beam not lighting up and it was a corroded wire that needed a new connector. Dont know If I would have even tried to do this fix but it was easy with this info and Pictures
 
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Here's a link to a post (#4) I made on the thread I started after I was unable to find this article. It may help someone who is looking here for a solution to a problem similar to the one I had. It also describes a troubleshooting procedure to avoid, since I unnecessarily went through a lot of time and effort before I attempted the fix that I should have tried first, before removing several items just to get to the fuses and relays to start checking things out with a multimeter. The wiring diagram and the failure I had led me to the conclusion that the failure was caused by a switch problem before I even started taking anything apart, but I failed to follow my instinct and just made it harder for myself.
 
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Could anyone help out with a problem I am having.

My bike's right headlight will not turn on. There seems to be a "sweet spot" in between the flipping of the dimmer switch, where the brights on the right headlight will turn on. However, if I let the switch go all the way, the right bright headlight will turn off, and only the left bright headlight will work. It appears that I need to have both parts of the switch engaged at the same time in order for the right bright headlight to work. Is there something I can do?

The left headlight works as it should: dim when on dim, and bright when on bright. The problem comes into play when dealing with the right bright headlight.

I did replace the headlight bulbs to newer, brighter LEDs last year. However, I don't think that has anything to do with it, since the left headlight works fine.
 

woodybelle

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Grebis10, if the left high beam works them the switch is sending out 12 v to the left high beam relay and the right high beam bulb. If you unplug the right headlight and check for 12v at the blue wire, you should have voltage there or the wire is broken or shorted between the switch and the right high beam connector. If you do have 12v then you have a bad bulb.
 
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Grebis10, if the left high beam works them the switch is sending out 12 v to the left high beam relay and the right high beam bulb. If you unplug the right headlight and check for 12v at the blue wire, you should have voltage there or the wire is broken or shorted between the switch and the right high beam connector. If you do have 12v then you have a bad bulb.
woodybelle, I checked the readings going to the plug for the headlight and everything was fine: no shorts and 12 V to blue when the brights are on and 12 V to the white when the dims are on. I also replaced the bulb and the same problem occurred. It seems that for the brights to work on the right headlight, that the dimmer switch needs to be engaging both the high and low beam circuits at the same time for the right headlight to come on. Any reason for this?
 

woodybelle

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Grebis the reason I ask about the lo beam is that you possibly have a bad ground. Why don't you try jumping a ground wire from the green wire on the right headlight bulb connector to the negative terminal on the battery and see if that fixes your problem.
 

yuergenb

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Oh my goodness. I am so confused now. I love all the ideas and suggestions, and have changed motors and rebuilt bikes but this is getting me. Not sure if any original posters or repliers are still on here, but my issue my left light blows the 10 amp fuse. I tried a 15. It went on low beam and high beam but cut out after a few seconds. My right headlight only works on low beam. Turn on high beam and it blows a fuse. Pretty baffled about where to start.
 
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