jfheath
John Heath
A Circuit Diagram showing the odd configuration of the ST1300 headlights, with some explanation.
The circuit is taken from a UK 2009 ABS model - from 2004 headlamps are on all of the time, there is no light switch on the handlebar console.
However, the UK spec models have a 'pass' switch to flash the main beam. USA vehicles and various others do not have this part of the circuit.
Contrary to what I believe to be common practice, the twin headlights on the ST1300 are not operated by relays in the conventional manner.
Instead, the circuit draws power from three different fused circuits.
I should add that the earth for the relays and the bulbs are shown separately - just to keep the diagram tidy. In fact they are all wired to a ground point, but they do not necessarily take the same route.
Edit 22 Aug 23:The relay grounds go through the yellow, multiway ground connector near the right hand mirror fixing bracket, behind the headlight. The headlight grounds do not.
There are a couple of errors in my copy of the 2004 Uk Honda circuit diagram. The hi and low beam filaments are drawn incorrectly, and the left and right relays are incorrectly labelled. As a result, following any single circuit, eg the Blue wire for the right hand main beam makes very little sense. Maybe later editions of the manual do not have this oddity, but my bike matches the two excellent coloured circuit diagrams available on ST-Owners. And the diagram above is correct for my Uk St1300A9.
The passing switch is an integral part of the Hi/Lo beam rocker type switch. However, none of the on-line coloured diagrams that I have seen show how this is wired. The diagrams in my Honda Workshop Manual show it, but there are so many errors on that, it is difficult to know what is right and what is wrong. The above diagram corrects an error in the official diagram in the cable colour for the hi beam passing switch.
For high beam, the switch is rocked forward from the low beam position, and for passing it is pressed back against a spring from the dipped position. Pressing pass keeps the low beam filaments turned on, and additionally injects power from a 3rd fuse - the one labelled Pass, Horn, Stop - to the Right hand Hi Beam circuit - which in turn triggers relays for the left hand main beam. As a result, when the lights are on, the passing switch causes both filaments to be turned on in both bulbs. There are two fuses for the headlights - 1 for the right hand bulb, one for the left hand bulb. When the passing switch is pressed the low beam is already drawing 55w and then the main beam draws 60w. So the LH headlight fuse is supplying power for both filaments and is almost at capacity when the passing switch is pressed. The right hand bulb is getting its power from two different sources when the passing switch is pressed.
The reason for doing this was that I was trying to establish the current drain on each of the fuses. I was particularly concerned with fuse C (abs model) because it feeds into the accessory quartet harness, and may limit the available power. See this thread for that information (post #6).
Just for interest - this is a table of which parts of the headlight circuit are active when different combinations of the 3 fuses are inserted and removed.
For completeness here are links to the coloured circuit diagrams - both of which show the correct wiring and labelling for the headlight circuit, but neither show how the pass button is wired.
@Anna'sDad - Rev 7 - (3) Article [13] - ST1300 - Wiring Schematic | ST1300 Articles | ST-Owners.com (st-owners.com)
Excellent schematic, easy to follow. Some labels difficult to read. I use this one most of the time.
@SpikingJC - 7 Diagrams - (3) Article [13] - ST1300 - Wiring Schematics for 03-07 Standard | ST1300 Articles | ST-Owners.com (st-owners.com)
Different diagrams for different years and models. These use dotted lines to represent the two-coloured wires and I find them less easy to follow a single cable. But the layout makes it easier to locate individual components - the diagram shows the components closer to the location on the bike, the labels are easier to read when zoomed in, and the diagrams show the location in the circuit of the multiway earth connectors - which are not shown on the Honda wiring diagrams that I have (A3/A4). I use this to confirm what I understood from AnnasDads diagram !
The circuit is taken from a UK 2009 ABS model - from 2004 headlamps are on all of the time, there is no light switch on the handlebar console.
However, the UK spec models have a 'pass' switch to flash the main beam. USA vehicles and various others do not have this part of the circuit.
Contrary to what I believe to be common practice, the twin headlights on the ST1300 are not operated by relays in the conventional manner.
Instead, the circuit draws power from three different fused circuits.
- The right hand headlamp is powered directly from one fuse, passing through the beam dip switch for high and low beam.
- The left hand headlamp draws power from a different fuse. The left handlamp beams are switched by two relays - one for high beam, one for low beam. The relays are triggered by the power feeds to the right headlamps.
- The Pass switch feeds into the right hand headlamp circuit from a third fuse. This bypasses the light switch if there is one, and also bypasses the cutout switch at the starter motor button, which normally cuts power to the headlights when the start motor is activated.
I should add that the earth for the relays and the bulbs are shown separately - just to keep the diagram tidy. In fact they are all wired to a ground point, but they do not necessarily take the same route.
Edit 22 Aug 23:
The diagram for my 2009 model shows that the relay grounds are all connected at a Pink 20P connector, not the yellow. The headlights ground passes through the white 24P multi-way connector. Both use green cables, both earth at the main earth point on the frame under the rear of the fuel tank.
Diagrams for pre-2008 models suggest that there is no connector joining the green earth leads - earths are just spliced into the harness. I don't believe that this is correct though.
The realities are therefore still a mystery to me for other models.
There are a couple of errors in my copy of the 2004 Uk Honda circuit diagram. The hi and low beam filaments are drawn incorrectly, and the left and right relays are incorrectly labelled. As a result, following any single circuit, eg the Blue wire for the right hand main beam makes very little sense. Maybe later editions of the manual do not have this oddity, but my bike matches the two excellent coloured circuit diagrams available on ST-Owners. And the diagram above is correct for my Uk St1300A9.
The passing switch is an integral part of the Hi/Lo beam rocker type switch. However, none of the on-line coloured diagrams that I have seen show how this is wired. The diagrams in my Honda Workshop Manual show it, but there are so many errors on that, it is difficult to know what is right and what is wrong. The above diagram corrects an error in the official diagram in the cable colour for the hi beam passing switch.
For high beam, the switch is rocked forward from the low beam position, and for passing it is pressed back against a spring from the dipped position. Pressing pass keeps the low beam filaments turned on, and additionally injects power from a 3rd fuse - the one labelled Pass, Horn, Stop - to the Right hand Hi Beam circuit - which in turn triggers relays for the left hand main beam. As a result, when the lights are on, the passing switch causes both filaments to be turned on in both bulbs. There are two fuses for the headlights - 1 for the right hand bulb, one for the left hand bulb. When the passing switch is pressed the low beam is already drawing 55w and then the main beam draws 60w. So the LH headlight fuse is supplying power for both filaments and is almost at capacity when the passing switch is pressed. The right hand bulb is getting its power from two different sources when the passing switch is pressed.
The reason for doing this was that I was trying to establish the current drain on each of the fuses. I was particularly concerned with fuse C (abs model) because it feeds into the accessory quartet harness, and may limit the available power. See this thread for that information (post #6).
Just for interest - this is a table of which parts of the headlight circuit are active when different combinations of the 3 fuses are inserted and removed.
For completeness here are links to the coloured circuit diagrams - both of which show the correct wiring and labelling for the headlight circuit, but neither show how the pass button is wired.
@Anna'sDad - Rev 7 - (3) Article [13] - ST1300 - Wiring Schematic | ST1300 Articles | ST-Owners.com (st-owners.com)
Excellent schematic, easy to follow. Some labels difficult to read. I use this one most of the time.
@SpikingJC - 7 Diagrams - (3) Article [13] - ST1300 - Wiring Schematics for 03-07 Standard | ST1300 Articles | ST-Owners.com (st-owners.com)
Different diagrams for different years and models. These use dotted lines to represent the two-coloured wires and I find them less easy to follow a single cable. But the layout makes it easier to locate individual components - the diagram shows the components closer to the location on the bike, the labels are easier to read when zoomed in, and the diagrams show the location in the circuit of the multiway earth connectors - which are not shown on the Honda wiring diagrams that I have (A3/A4). I use this to confirm what I understood from AnnasDads diagram !
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