Help diagnosing headlight issue

[jodog]

As I was riding home in the dusky hours I noticed my aux lights would not switch to high beam. My stock lights would, and my aux lights are tapped into the high beam wire near the headlights. BTW I have LED headlights and the aux lights are wired independently of stock wiring except for the high beam trigger wire.

Upon inspection at home, I find that the left side (as you sit) headlight is not working. After dissassembling the bike I tested the headlight and it works, and I have no voltage coming from the stock wire connector. The wire feeding the left headlight seems dead.

Any ideas?

Bob

 

[Uncle Phil]

Mice maybe chewed the wire into?
Bad ground somewhere in the circuit?

 

[JohnK]

I’d agree with Uncle Phil also at each connection trace back for live voltage, I found burned or chewed wire that grounds or has been broken creating an open. Along with loose connectors.

 

[jodog]

Since the low beam wire and the high beam wire are dead, I assumed that it wouldn't be a single wire Mouse-chewed, but something more like a loose ground or a fuse.

Q: are the left and right headlight circuits independent? The right side is working fine on both lo and hi beam.

Bob

 

[jodog]

Oh, and does anyone know which fuses to check and where the grounds might be located?

 

[Nexus]

Could also be the relay. there is a separate relay for the left and right.
View media item 417This is for the police version, but I think it should be the same. Fuses E & I in the fuse box are for the headlight (doesn't say which is which). I would check those.

 

[Larry Fine]

You need to follow a wiring diagram and test for power at each available point starting at the fuses.

I recommend using a probe-type tester instead of a voltmeter for almost all power troubleshooting.

You can clip the wire to battery - or ground to test for hots and clamp it to +12v to test for grounds.

 

[jfheath]

St1300 right headlight comes on with a the switch. The Left headlight is triggered by the wiring to the right via 2 relays one for high, one for low. The left bulb has a separate circuit is fed from a separate fuse

Details here.

Article [13] - ST1300 - Headlight Circuit | ST1300 Articles

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...

www.st-owners.com

 

[dduelin]

Take a low key approach and procure a piece of at least 16 gauge wire about 18" long. Bare both ends about 1/4" and if the wire is stranded twist the bare wires together and make a point. The wiring connector to the back of the left headlight bulb has three wires leading to it. Find the solid green one and insert one end of your test wire into the connector so it makes contact with the metal clip inside the connector for the green wire. This is the ground wire for that headlight bulb. With the key ON take the other end of the test wire and make a good contact against the frame behind the steering head. A lot of ST1300 ground issues start with the left headlight losing a good ground connection so test it to rule out ground issues in various connectors between the left headlight and the frame ground. Obviously have a known good bulb in the left headlight.

 

[ad.hom]

While you have the bike apart, check the H4 connectors on the back of the OEM headlights and the loom connector under the left tupperware.

In my case, the H4 connector had melted (but I also got the main beam indication when I wasn't running main beams). I put new H4 pigtails in, and beefed up the ground from front to rear - no problems since.

 

[Igofar]

Standing by the

 

[JoeP]

Could also be the relay. there is a separate relay for the left and right.

+1

I'd bet it is the relay. My '04 had the same issue years ago. Turned out to be the relay.



Wiring diagram - see post 22 for the correct diagram

Article [13] - ST1300 - Headlight Wiring Diagram | ST1300 Articles

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.

www.st-owners.com

 

[jfheath]

If you suspect a relay, switch out the suspect one with one of the others - say, the fuel pump relay. I think the only one that is different in that relay cluster is the indicator relay. But check the printing on the side if you are unsure.

 

[jabbott]

Resurrecting this thread, as I had my left headlight go out in the middle of the IBR. I found a blown fuse in the "rear" fusebox on the left side, and the replacement blew instantly upon contact. Since time was tight, and my right headlight still worked along with the LED marker lights, I was confident I'd be seen by other motorists. My aux lights on a separate circuit took care of open roads at night. Hoping it's just a relay. Will tear into the bike this weekend, wondering what you found when you had this issue, @jodog ?

 

[Obo]

Resurrecting this thread, as I had my left headlight go out in the middle of the IBR. I found a blown fuse in the "rear" fusebox on the left side, and the replacement blew instantly upon contact. Since time was tight, and my right headlight still worked along with the LED marker lights, I was confident I'd be seen by other motorists. My aux lights on a separate circuit took care of open roads at night. Hoping it's just a relay. Will tear into the bike this weekend, wondering what you found when you had this issue, @jodog ?

Replacement fuses blowing instantly lead me to think there's a short somewhere.

 

[Larry Fine]

Instant fuse blowing means a direct short to ground. Look for physical wiring damage.

There's also a chance that there is an internal short inside the bulb itself, so disconnect it.

Troubleshooting tip: temporarily wire a high-wattage incandescent bulb in place of the fuse.

It will do double duty as an indicator, and as a current limiter so you can keep the power on.

 

[jodog]

Resurrecting this thread, as I had my left headlight go out in the middle of the IBR. I found a blown fuse in the "rear" fusebox on the left side, and the replacement blew instantly upon contact. Since time was tight, and my right headlight still worked along with the LED marker lights, I was confident I'd be seen by other motorists. My aux lights on a separate circuit took care of open roads at night. Hoping it's just a relay. Will tear into the bike this weekend, wondering what you found when you had this issue, @jodog ?

Bad ground. In an unrelated story, just before the IBR my upper aux lights stopped working in hi and lo beam. Next day they worked just fine and have ever since. Voodoo.

 

[jabbott]

Bad ground. In an unrelated story, just before the IBR my upper aux lights stopped working in hi and lo beam. Next day they worked just fine and have ever since. Voodoo.

Thanks, Bob. So was it the ground wire coming off the left headlight connector, or the ground coming off the relay? Thanks!

 

[DannoXYZ]

Not bad ground. Here's logic on how fuses work:

1. they blow when more current flows than their rating

2. current flows from power to ground (traditional model)

3. IF you had bad ground, LESS current would flow than normal and fuse won't blow

4. you've probably got short, meaning unauthorised power wire is flowing into GOOD ground. Caused by improper connection or exposed power wires touching frame or ground wire.

Easiest way to find short is with meter. This is 5-minute with meter... or less in many cases. Pull bulb and measure impedance to verify it's not source of short.