Headlamp Flasher

eo1bart · Aug 30, 2021

I recently finished the rebuild of my '74 Roadster, including a complete rewire. Everything is working as it should except when I push the headlamp flasher button on the handlebar switch, it instantly blows the main fuse at the battery. Both the high beam and low beam work indepently and I'm getting 12.8 volts for both at the headlamp. Any ideas?

L.A.B. · Aug 30, 2021

The LH cluster upper button?

850commando · Aug 30, 2021

what is the fuse rating? what headlight do you have installed? if you have an H4 headlight and both high and low beam come on together when you flash, you would have in the order of 115w, say at 13v you may need a 15amp fuse...

eo1bart · Aug 30, 2021

L.A.B. said:
The LH cluster upper button?

Yes headlamp flasher, though I have mine switched to the right side of handlebar so that it is consistent with my other bikes.

eo1bart · Aug 30, 2021

850commando said:
what is the fuse rating? what headlight do you have installed? if you have an H4 headlight and both high and low beam come on together when you flash, you would have in the order of 115w, say at 13v you may need a 15amp fuse...

I am using a 20amp inline mini fuse and a Hella Halogen headlamp, Model;

002395301 High/Low Beam (SAE/DOT), 1 HB2/9003 12V 60/55W Bulb

Amazon product ASIN B0002M9QK6

L.A.B. · Aug 30, 2021

eo1bart said:
Yes headlamp flasher, though I have mine switched to the right side of handlebar so that it is consistent with my other bikes.

Does the fuse blowing happen when the headlamp is switched off? Only when it is on? Or both?

As the headlamp flasher button switch connects white to blue/white (main beam) inside the switch cluster then pressing the switch button with the headlamp off would seem to be shorting white to ground.

eo1bart · Aug 30, 2021

It pops the fuse when I have the headlight on and press the flasher button. I have not tried it with the headlamp off. I will do that tonight and report back.
Like you said the symptoms appear to be a short to ground. I did separate the handle bar switch cluster and did not see any obvious problems though

Thanks Bob

Headlamp Flasher

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