Headlight circuit fuse

1602 Views 16 Replies 10 Participants Last post by bahn88, Apr 2, 2022

drav77

Discussion Starter · Mar 25, 2022

the 10A fuse on my headlight circuit has recently started blowing. When I replace it it works for maybe 2 or 3 rides, then blows the fuse. It's been a little intermittent so sorta tough to trace down.

I do have a DMM but am admittedly new to using it but know some basics.
Anyone have a few tips on certain connections I might start at with the multimeter to try and narrow this down a little?

Planning on checking the hi/low beam switch for corrosion,
and the current flowing through the fuse for a start.
(it is breaking the actual wire inside the fuse, when they pop I can see the wire inside failing which tells me too much current?? lose ground?? frayed wire??)

any tips appreciate !!!!

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Gerard

· #2 · Mar 25, 2022

Check the wires going through the steering head area that they havent broken and shorting out on the frame.

Reactions: 1

reclinedrelic

· #3 · Mar 25, 2022

When the fuse actually blows it is due to high current. High current is almost always due to a short circuit. A short circuit will occur when a wire conducting electricity touches a ground, the frame for example.

To track down a short circuit replace the fuse with a 12 volt light bulb. The bulb will light when there is a short circuit. Try moving wires to see if you can cause the short or cause it to go away if present.

Look for wires where you can see bare wire, insulation worn away or melted or chewed by rodents.

Reactions: 1

drav77

Discussion Starter · #4 · Mar 26, 2022

measured 13.4v across the fuse location... same at battery direct. I wouldn't think that would blow the fuse ?? I'll keep searchin

DouginEasternWashington

· #5 · Mar 26, 2022

drav77 said:
measured 13.4v across the fuse location... same at battery direct. I wouldn't think that would blow the fuse ?? I'll keep searchin

Take Gerard’s advice. Look close for bare wire that could be contacting anything metal and shorting out.

Randall-in-Mpls

· #6 · Mar 26, 2022

drav77 said:
measured 13.4v across the fuse location... same at battery direct. I wouldn't think that would blow the fuse ?? I'll keep searchin

Voltage doesn't blow fuses. Amperage does.

Reactions: 1

Sidecar Bob

· #7 · Mar 26, 2022 (Edited)

Do what reclinedrelic said with a light bulb. It should light when the headlight is turned on but won't be full brightness unless the short is present The bulb should be an 1156 or something similar (too small a bulb can have confusing results because it has much higher resistance than some normal loads). Don't worry about not having a fuse in the circuit when you connect the bulb because the bulb will limit the current to a safe level.

Re learning how to use your multimeter: A multimeter is basically a number of meters for measuring different things combined into one so it is best to learn what each type of meter does first and this page has a good explanation of that. Once you have read about the various types of meters click Multimeters near the bottom for the page on how to use them

Meters, voltmeters and ammeters | Electronics Club

Learn how to connect and read voltmeters and ammeters, both digital and analogue types.

electronicsclub.info

This page on what series and parallel circuits are and how they work is also recommended reading

Series and Parallel Connections | Electronics Club

Learn what the terms series and parallel mean in electrical circuits.

electronicsclub.info

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Reactions: 1

drav77

Discussion Starter · #8 · Mar 26, 2022

Thanks so much you guys are always so helpful! Really appreciate your expertise.
AND... I think i might have found the guilty party... This would do it I would imagine... It was resting against the bottom of the lower triple, and it's in the headlight circuit. (see below image)

Automotive tire Light Coil Motor vehicle Hood

Product Rectangle Slope Schematic Font

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Gerard

· #9 · Mar 26, 2022

That would do it

Randall-in-Mpls

· #10 · Mar 26, 2022

Ideally, you'll get a couple layers of heat shrink on each of those. That will involve clipping and rejoining the wires.
At least wrap each wire with self-sealing silicone tape.

Reactions: 1

rcw3586

· #11 · Mar 31, 2022

Something has crushed those two wires. While you are repairing them figure out what caused the problem in the first place and fix that too. They may be getting pinched when the steering is at its limits.

Reactions: 1

Blurredman

· #12 · Mar 31, 2022

Had the same thing a couple of years back.

Wire was caught in the steering lock for me though. So it was a bit more obvious to me, as the light stopped working when I turned left..

bahn88

· #13 · Mar 31, 2022 (Edited)

Yah....i had a Bmw where the ignition would cut out each time the bars would turn....eg going roundabouts or sharp corners...the rider roadside assist wouldnt help cause they said the bike was RIDEABLE...
Ended up being a frayed wire at steering head...5 min fix...

drav77

Discussion Starter · #14 · Mar 31, 2022

rcw3586 said:
Something has crushed those two wires. While you are repairing them figure out what caused the problem in the first place and fix that too. They may be getting pinched when the steering is at its limits.

Yessir! exactly right. Got stuck in the turn stop I'm guessing. I since wrapped it and rerouted it so that wouldn't happen again.

Randall-in-Mpls

· #15 · Mar 31, 2022

bahn88 said:
Yah....i had a Bmw where the ignition would cut out each time the bars would turn...

The Grub was doing the same a couple years ago. There was a kink in a wire inside the main harness just behind the steering head. No wear on the insulation, but each time the handlebar was turned hard left, the wire would flex at the kink and fray a little more.
Finally, it gave out completely while I was searching for the fault. I spliced in a short piece of new wire, heat shrinked and rewrapped, and all is good.

richnct

· #16 · Apr 1, 2022

When I searched “Roadside Assist” on my phone it only returned my own number. 😆

Reactions: 1

bahn88

· #17 · Apr 2, 2022

richnct said:
When I searched “Roadside Assist” on my phone it only returned my own number. 😆

Yeah...twas a new BMW...so i thought id just score a "free trailer ride" to the dealer.
The roadside assist was a freebie i didnt renew

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