help please chasing down an electrical gremlin in my headlights

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flip-flop

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Joined
Dec 3, 2008
Messages
24
Location
Hobe Sound, Fl.
Bike
2006 ST1300
My 2006 1300 has an issue when using the high beams. Toggling the high beams on- no problem, both high beams work. Flipping the switch back to low beams and 50% of the time the headlights will go out completely (high and low beams) until I very lightly press the high beam switch again at which point the low beams come back on.

Since the Florida weather is pretty harsh on electrics, I assumed the switch itself was the issue. I replaced the entire left side switch assembly but that did not resolve the issue.

At this point, I am hesitant to use my high beams as I am worried that sooner or later I will lose all!

Could it be a relay? And if so, which one amongst the cluster of relays on the left side?

Thanks for your ideas!
 
Any other strange electrical activity? Does the high beam indicator in the dash stay on even when the high beams are not on?

Could be a relay but older ST1300's are known to develop ground circuit problems. There is connector behind the left side fairing above the cylinder head. All of the ground wires for the front of the motorcycle pass through the green ground wire in this connector. It is often found overheated and melted causing all kinds of electrical havoc. There is another one behind the right-hand headlight- same thing but less common. I would first check the integrity of the ground paths.
 
Andrew Shadow said:
Any other strange electrical activity? Does the high beam indicator in the dash stay on even when the high beams are not on?

Could be a relay but older ST1300's are known to develop ground circuit problems. There is connector behind the left side fairing above the cylinder head. All of the ground wires for the front of the motorcycle pass through the green ground wire in this connector. It is often found overheated and melted causing all kinds of electrical havoc. There is another one behind the right-hand headlight- same thing but less common. I would first check the integrity of the ground paths.
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I just went out in the garage and cycled the high beams about 25 times. The first 8 or 10 times I had no low beams when cycling from high back to low. I would lightly press the high beam switch and they'd come on. Interestingly, after the first 8 or 10 times though they cycled normally without issue, low to high and back to low.

When I cycle from high back to low beams the dash indicator goes out. I can hear the relay cycling with each action.
 
When you actuate the hi/lo switch, power switches from the white wire (for High) to the blue wire (for low). Each of those actuates the specific relay that drives that set of filaments. For the low beams to not come on quickly has to be either the switch or the relay, and given that working the switch a bit fixes things, the switch still seems like the most obvious location, sticky grease might be slowing down the connection. You can also physically swap the high and low relays, if the problem moves to the high beams, that would make a dodgy relay the likely culprit.
 
Mellow said:
Have you sprayed the switches w/contact cleaner or opened up the housings and spray them? It's comment for gunk to build up there.
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Joe, I replaced the entire switch assembly on the left and right sides. Housing and switches- the Florida sun was eating the housing up!
 
TerryS said:
You can also physically swap the high and low relays, if the problem moves to the high beams, that would make a dodgy relay the likely culprit.
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Can you detail which relay is which? I didn't see anything marked high or low beams and all those relays under the seat look the same?
 
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Relay locations - the high and low beam relays are for the left bulb only. The power for the left bulb comes from a different fuse from the power for the right bulb.

Take a look at the diagram at this link
https://www.st-owners.com/forums/threads/st1300-headlight-circuit.175199/

I’ll repost the image below.

It is from a Uk ST1300A9 - so it has an extra powered input for the flash to pass switch, so ignore the dotted blue line which comes from the middle of the 3 fused connection labelled Horn, Pass, Stop.
The USA bikes don’t have this.

The wiring diagram in the manual is difficult to follow - especially since it is not accurate !

In essence, if power isn’t getting to the right hand bulb, the left hand bulbs cannot be switched on by the relays. The right hand bulbs don’t use relays. So by removing fuses, you should be able to work out where the fault lies.


1782949256328.jpeg
 
jfheath said:
1782948522472.png

Relay locations - the high and low beam relays are for the left bulb only. The power for the left bulb comes from a different fuse from the power for the right bulb.

Take a look at the diagram at this link
https://www.st-owners.com/forums/threads/st1300-headlight-circuit.175199/

I’ll repost the image below.

It is from a Uk ST1300A9 - so it has an extra powered input for the flash to pass switch, so ignore the dotted blue line which comes from the middle of the 3 fused connection labelled Horn, Pass, Stop.
The USA bikes don’t have this.

The wiring diagram in the manual is difficult to follow - especially since it is not accurate !

In essence, if power isn’t getting to the right hand bulb, the left hand bulbs cannot be switched on by the relays. The right hand bulbs don’t use relays. So by removing fuses, you should be able to work out where the fault lies.


1782949256328.jpeg
Click to expand...
You are a never ending source of truth, John! I did not realise that the relays only drive one side. That does help with the diagnosis though. If both sides don't work, it can't be a relay fault, because a faulty relay would only affect the left side, not the right. For both low beams to fault out, the switch is the only common point?
 
Thinking out loud here. The hi/low beam switch switches the main power to either the right hand high beam or the right hand low beam. It can never connect both hi and low circuits together. That suggests that there is a point in between where neither is connected.

But you replaced the switch, and the behaviour did not change.

So either the new switch had the same fault - unlikely, but possible - or the fault is elsewhere. So where could that be ?

One possibility is the starter motor button. The right hand bulb power passes through the starter button, so that lights are turned off when starting the bike. You can use that to flash lights at night time.

Another possibility is the circuit or connectors that feed the handlebar switch. Worth looking at - but first take a look at the fuses that feed the headlights. We are looking at the right hand circuit but to save worrying about which one is which, check both.

Take them out and clean the spade connectors. And insert, remove, inset a few times to clean up the fuse holder contacts. Remember that some of the fuse box is always live whether ignition is on or not. Some power is turned on by the ignition key switch. I’ve forgotten whether the light circuits are. I gave my manuals to my brother along with the bike.

The connectors - check the state of the wiring entering the rear of the connector. Look for verdigris, damaged insulation. Check the female terminals. The males should be a tight fit. Check that they are not a sloppy fit inside the casing - and for any sign that the male spade is sliding down the outside of the female terminal. I’m talking generally here - I have never disconnected the handlebar switch but I have just been looking at the photos for that part, they look to have the standard hitachi style connectors with 2.8mm blades - which is what I was imagining.

Unplug the two relays. What is the behaviour like then ? Are there any signs that additional equipment has taken its power from the headlight wiring eg driving lights?
The headlight circuits don’t have enough capacity to provide power for (say) driving lights. Something may have melted.

Some inconsistent behaviour can arise if the element inside the bulb has broken and one end of it is dangling and is touching the other element. It can even weld itself in place ! It doesn’t sound like that is the issue here though.
 
I had a similar looking problem with the relay for my auxiliary lights and accessories. Even though the relay clicked, nothing happened, so I had to toggle the switch a few times to turn the lights on. I replaced the relay and the problem disappeared. When I cut the old one open, I found oxidation and what looked like pitting or material build-up on the contact surface.
 
Yes it does. Thats why I mentioned the starter motor button a couple of posts back - as the power for the right hand bulb is cut when the button is pressed. (Which also turns off the relay for the left hand bulb).
 
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