Article [13] ST1300 - Headlight Wiring Diagram

MileHigh

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Just an easier to read headlight wiring diagram for the ST1300 (non P model)

This is a copy of the Honda service manual, wiring diagram.

It is wrong!

The relay names are reversed and, the lamp filament positions are reversed.
8122.jpg
See post #22 for correct wiring and, additional information.

 
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Re: ST1300 headlight wiring diagram

Nice... That's sure easier to read than the one in the manual..
 

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Re: ST1300 headlight wiring diagram

Indeed. Mid if I put that on STWiki?

--Mark
 
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Re: ST1300 headlight wiring diagram

Just an easier to read headlight wiring diagram for the ST1300 (non P model)

This is a copy of the Honda service manual, wiring diagram.

It is wrong!

The relay names are reversed and, the lamp filament positions are reversed.


See post #22 for correct wiring and, additional information.
Power to Right is straight through switch, while Left is relayed?

Is it the explanation for Left burnout?
 
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MileHigh

MileHigh

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Re: ST1300 headlight wiring diagram

Power to Right is straight through switch, while Left is relayed?

Is it the explanation for Left burnout?
What I'm trying to figure out is the logic behind the way Honda wired the system. Relays for one side, switch for the other side.

I have re-checked the wiring diagram in the service manual (2005) several times before I re-drew it and even a few times afterwords.

My drawing is just easier to read. My question is, why does just the left lamp use a relay?

I can understand using a relay. Auto manufacturers have used headlamp relays for years. A relay will handle a larger load than a switch and, not melt the switch & dash.

I thought maybe Honda was attempting to add some redundancy in case a relay or switch malfunctioned. Not so if the switch fails. If the switch fails, the relays wont operate and, you have no headlights.

If a relay fails, you would still have right side, low & high beam powered through the switch.

Switches usually fail before a relay does. At least in my experience.

The other item that has me perplexed is, when the switch is in the low position, it activates the Hi relay and, vis a versa.

Could be a misprint in the manual but, I checked all 4 diagrams and they are all the same.

Interesting....:think1:
 

Mark

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Re: ST1300 headlight wiring diagram

Let me see...
Relay on the left side and which light does the ST1300 lose?
Oh yeah... the left...
:shrug1:
 
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Re: ST1300 headlight wiring diagram

What I'm trying to figure out is the logic behind the way Honda wired the system. Relays for one side, switch for the other side.


I can understand using a relay. Auto manufacturers have used headlamp relays for years. A relay will handle a larger load than a switch and, not melt the switch & dash.

Interesting....:think1:
Aren't you answering the question right there?

Two bulbs could be too much load through the switch, so to power a second one, it would have to be relayed?

Why not relay both?

a) Maybe to save a few cents

or b) according to wikipedia on relays, "If the coil is energized with DC, a diode is frequently installed across the coil, to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to circuit components. Some automotive relays already include that diode inside the relay case.". So maybe Honda knows that somehow they do not control the spike well enough, reducing the left bulb's life, and they chose to leave the right unrelayed?
 
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Re: ST1300 headlight wiring diagram

What I'm trying to figure out is the logic behind the way Honda wired the system. Relays for one side, switch for the other side.


The other item that has me perplexed is, when the switch is in the low position, it activates the Hi relay and, vis a versa.

Could be a misprint in the manual but, I checked all 4 diagrams and they are all the same.

Interesting....:think1:
Would be interesting to check if it is actually wired that way! Doesn't make much sense.
 

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Re: ST1300 headlight wiring diagram

Honda may have goofed with the diagram. See this thread.
 
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Re: ST1300 headlight wiring diagram, Jim Davis, EasternBeaver

Dear ST-Owners,

Our friend Jim Davis, at EasternBeaver (Custom harnesses, Relays etc), and former 1100 rider, is offering to have an expert look at that.

Could somebody send him a copy of the original wiring diagram, for him to review?

Would do it myself, but my manual is loaned out.

His eMail is:

"James B. Davis" <jim@easternbeaver.com>

Thanks.
 

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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! ;)
 
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MileHigh

MileHigh

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Re: ST1300 headlight wiring diagram

Well...EasternBeaver/Jim looked at the diagram and seems as puzzled as we are!
To me, it looks like Honda mislabeled the relays in the service manual diagrams.

I have a set of new lamps on the way-

http://www.powerbulbs.com/product_detail.asp?prod=111

I am going to perform some "on the bike" verifications of lamp filament, wiring and, relay connections.

Will post findings and up-dates very soon.
 
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Re: ST1300 headlight wiring diagram

To me, it looks like Honda mislabeled the relays in the service manual diagrams.

I have a set of new lamps on the way-

http://www.powerbulbs.com/product_detail.asp?prod=111

I am going to perform some "on the bike" verifications of lamp filament, wiring and, relay connections.

Will post findings and up-dates very soon.
This is one thing Jim did recommend, OSRAM. He indicated there is a Long Life version of the H4 he tested and is pleased with (luminosity wise). Interested in how you like your find.
 
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