Headlights out

I got on my ST1300 to ride home from my parents tonight and the headlights were out. I didnt have time to trouble shoot so I rode my Dads 09 RT Home. Nice bike but I'll be glad to get back on the ST. So any thoughts on the lights? Hopefully its just a fuse.

Jeff

If it's both, yeah I'd think a fuse first..

Yes both are out.

Hey Jeff,

Here is how the headlights are correctly wired & powered for the ST.

If both are out, check fuse D or E. Otherwise, it's the starter (switch) or dimmer switch.

Could also be bad bulbs but, both at the same time is unlikely.

https://www.st-owners.com/forums/showpost.php?p=706872&postcount=22

MileHigh said:

Hey Jeff,

Here is how the headlights are correctly wired & powered for the ST.

If both are out, check fuse D or E. Otherwise, it's the starter (switch) or dimmer switch.

Could also be bad bulbs but, both at the same time is unlikely.

https://www.st-owners.com/forums/showpost.php?p=706872&postcount=22

Click to expand...

That's a really good diagram, yours?
I was tracing the schematic and that's a pain.

CABINPETE said:

That's a really good diagram, yours?
I was tracing the schematic and that's a pain.

Click to expand...

Yupper.

iWork '09

Tracing the wiring diagram with bifocals just didn't do it for me. Had to make one I could read and, share with other visually challenged riders.

Also, since mother Honda can't seem to get it right in 5 odd years.:

Must have former GM employees writing & proof reading their service manuals.

MileHigh said:

Hey Jeff,

Here is how the headlights are correctly wired & powered for the ST.

If both are out, check fuse D or E. Otherwise, it's the starter (switch) or dimmer switch.

Could also be bad bulbs but, both at the same time is unlikely.

https://www.st-owners.com/forums/showpost.php?p=706872&postcount=22

Click to expand...

Interesting to see the wiring. My guess is that the left bulb blows first because it is burning slightly hotter (the relays are providing a lower resistance path to the 12V). The Right has to go through 2 switches which will probably have more contact resistance. Just some thoughts. I really don't know why Honda is using relays these days when a power FET would do a really good job.

Do you by chance have a headlight modulator installed that uses only one of the OEM headlight plugs? I lost all headlights using a Kriss modulator that was configured that way. Because it drew power for both lamps from only one of the OEM circuits, it overloaded and blew the 10A fuse. Such a design leaves both headlights susceptible to a single fuse failure, not safe.

Kisan and Comagination modulators use both OEM plugs, a better design.

OK, no blown fuses, modulator installed, the high beam indicator light doesnt work, the bike runs, all other lights work. Thanks MileHigh I'll proceed to the starter switch and dimmer switch.

Murphy is obvisually involved as today is a great day for riding.

Dont rule out the bulbs if you hit something like a pothole really hard. If its been a long time since the bulbs have been replaced then it might be a good idea to replace them anyway just to know the bulbs are good for the rest of your diagnosing. The headlght on my RT stopped all together once but it turned out to be a bad Kissan headlight modulatior. However after the diagnosis and putting everything back together one bulb didnt light up and all it was was a bad bulb. So sometime im my playing around that one bulb went bad.

Don't discount the possibility of a bad modulator. Try by-passing it.

I had a modulator go out and it "took-out" my headlights.

I have also had my starter button "stick" and kill the lights...... I just turned the key off and push the button a few times this "fixed" it.

MileHigh said:

Tracing the wiring diagram with bifocals just didn't do it for me. Had to make one I could read and, share with other visually challenged riders.

Click to expand...

Er, quick question about the power source for the right high beam filament: is it really drawing power through the starter switch rather than being relay fed like the left high beam filament? Shouldn't the horizontal line feeding the high beam indicator extend to the left to feed that filament rather than the supply dropping down from the "H" contact on the dimmer switch?

In any case, given that

Trike flyer said:

OK, no blown fuses, modulator installed, the high beam indicator light doesnt work, the bike runs, all other lights work. Thanks MileHigh I'll proceed to the starter switch and dimmer switch.

Click to expand...

high beam indicator does not work, I'd head for the starter switch first because 1) its easiest to get to, 2) debris/verdigris would easily keep the NC circuit from closing and lighting up the headlights.

I'm not sure what the construction of the dimmer switch is, but even if its an open switch like the starter switch, it would have to fail so that it was unable to close both high and low, which seems less probable to me.

Oh, and since I have no idea how the modulator is wired in, but if it modulates both high and low beams, I'd take it out before trying the starter switch.


Kind of a "last things first" approach.

There working!!!!! and in time for a afternoon ride.

The issue ended up being the starter switch. The switch was not fully returning and thus not allowing power back to the headlights. I cleaned and lubed the sticky switch and it is working fine.

The quality of advice from this site always impresses me. Thanks to MileHigh fir the clear wire diagram and advice.


Thx all
Jeff

CruisingDog said:

Interesting to see the wiring. My guess is that the left bulb blows first because it is burning slightly hotter (the relays are providing a lower resistance path to the 12V). The Right has to go through 2 switches which will probably have more contact resistance. Just some thoughts. I really don't know why Honda is using relays these days when a power FET would do a really good job.

Click to expand...

Reviewing some of the posts regarding the ST1300's headlight wiring revealed a really odd engineering design exercise. Why would they only use relays for one headlamp, rather than both of them? Why don't they have each headlamp circuit independently fused? The way the headlamps are wired, a short anyplace that blows either fuse D(E) or G(I) will leave the rider completely in the dark - no high or low beam from either headlamp! That strikes me as a major safety-related design flaw. Aren't the left and right headlights on most cars and trucks independently fused? I know they are on my Expedition, and think they may be on the wife's Grand Prix, as well. It looks to me like Honda could use some EE's on their design staff.

Rant over.

Don

Don B said:

Reviewing some of the posts regarding the ST1300's headlight wiring revealed a really odd engineering design exercise. Why would they only use relays for one headlamp, rather than both of them? Why don't they have each headlamp circuit independently fused? The way the headlamps are wired, a short anyplace that blows either fuse D(E) or G(I) will leave the rider completely in the dark - no high or low beam from either headlamp! That strikes me as a major safety-related design flaw. Aren't the left and right headlights on most cars and trucks independently fused? I know they are on my Expedition, and think they may be on the wife's Grand Prix, as well. It looks to me like Honda could use some EE's on their design staff.

Rant over.

Don

Click to expand...

Don,

It sounds like you have a fair idea of a solution. What exactly would be involved in implementing a more robust engineering solution?

Trike flyer said:

There working!!!!! and in time for a afternoon ride.

The issue ended up being the starter switch. The switch was not fully returning and thus not allowing power back to the headlights. I cleaned and lubed the sticky switch and it is working fine.

The quality of advice from this site always impresses me. Thanks to MileHigh fir the clear wire diagram and advice.


Thx all
Jeff

Click to expand...

Hey guys...
same thing here..Both lights went out, checked all fuses and light bulbs, all good. Cleaned and sprayed some cleaner in the starter switch, presto, all working. Thanks for the advice and feed back, saved me many hrs and dollars.
jesse