Headlight & Indicator Fuse Blowing when riding

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Swint78
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Headlight & Indicator Fuse Blowing when riding

Post by Swint78 » Tue Oct 29, 2019 7:36 am

Hi, my son has a 1999 L-9 ZXR400 which has developed a problem with the headlight and indicator fuses blowing but only when riding which is a bit of a inconvenience to say the least now the clocks have gone back!
Ticking over on the drive no problems at all but as soon as he’s out on the road within 1/2 a mile one or the other or both blow.
I have changed the voltage rectifier/regulator and tested with a multimeter and get 12v on tick over and 14v at 6000rpm which I thought sounds about right.
Has anyone come across the same or similar problem, or have an idea what to test next?

Thanks Andy


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banner001
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Re: Headlight & Indicator Fuse Blowing when riding

Post by banner001 » Tue Oct 29, 2019 6:31 pm

The fuse is blowing as there is too much current on the wires, I would be thinking a short circuit, aftermarket parts etc...
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JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003

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Re: Headlight & Indicator Fuse Blowing when riding

Post by banner001 » Tue Oct 29, 2019 6:45 pm

I dont know the l9 wiring, but I'm guessing it's similar to the l5, I've put up the colour diagram on here, when you say headlight fuse do you mean the 10a or 15a one?
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003

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Re: Headlight & Indicator Fuse Blowing when riding

Post by Ewetea » Tue Oct 29, 2019 8:05 pm

Hi. A few more thoughts: although the light switch is on the right hand side, the power is supplied to the headlights from the dimmer switch on the left hand side. The indicators are also controlled from that side, so have a look in that unit. Also, main beam is powered through a relay under the seat, and the indicators also work through a relay under the seat. The fact that everything works when the bike is on the drive, but not when a rider is on the seat may indicate that the problem lies there. This is not the weather to spend time looking for the problem, so maybe some temporary wires to keep things going?

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Re: Headlight & Indicator Fuse Blowing when riding

Post by Swint78 » Wed Oct 30, 2019 4:59 pm

Hi banner001, it is the 10amp blowing


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Re: Headlight & Indicator Fuse Blowing when riding

Post by banner001 » Thu Oct 31, 2019 7:14 am

OK, so on the L5 bikes the 10A fuse and Indicator fuse share a common rail which is the brown wire that goes from your ignition switch to your junction box and reg rec.

My guess would be that your issues lies in your junction box (internally shorting to ground), or the brown wire from your ignition switch to the junction box, or the white wire from the battery/reg rec to the ignition switch.

The only other area that they have somewhat in common is the LHS switchgear, though a fault here is a long shot.

Ex:: Can you get your son to go out in the day, remove the indicator and 10A headlight fuses but leave the bike with its lights ON and see if any other fuses blow, specifically the 10A ignition, horn or tail light fuses?

The Ex:: point above, if the other fuses blow then the issue is probably brown wire or junction box, if they don't then its possible that it could be grounding through the LHS switchgear.
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003

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Re: Headlight & Indicator Fuse Blowing when riding

Post by Swint78 » Thu Oct 31, 2019 12:36 pm

He’s going to try that now, talking about the left hand switch gear, when we try to switch high beam on the headlights go off altogether then back on with dipped beam, sounding more like the switch gear is at fault??


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Re: Headlight & Indicator Fuse Blowing when riding

Post by banner001 » Thu Oct 31, 2019 1:37 pm

Definitely sounds like it's grounding out somewhere, or is taking some alternate path.

With the light switch on the RHS set to off, press the high beam flasher button on the LHS switchgear, do the high beams flash?
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003

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Re: Headlight & Indicator Fuse Blowing when riding

Post by Swint78 » Sat Nov 02, 2019 9:40 pm

He has ridden for the last couple of days without the h/light and indicator fuse in place and nothing else has blown.
Also when the lights are switched off on the RHS switchgear the headlight flasher on the LHS still does not work.


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Re: Headlight & Indicator Fuse Blowing when riding

Post by banner001 » Mon Nov 04, 2019 7:43 am

Swint78 wrote:
Sat Nov 02, 2019 9:40 pm
Also when the lights are switched off on the RHS switchgear the headlight flasher on the LHS still does not work.
Did you put the 10A fuse back in for the headlights before doing this, as you would have needed to do so.

OK, what I suggest is you put all the fuses back and we test the systems in isolation.

Disconnect the LHS main block near the air box along with the 2 pin starter lockout box and the single bullet for the high beams.

Buy two 3x position switches (I. E. A common middle rail and then it sends power down one side or the other) these will be used to simulate your high low beam and indicators.

Wire up these switches to the LHS main block that's part of the loom (see below)

Fix switches to handlebars and go for a ride as normal.

Try and see if the fuse blows with a particular switch or combination of switches - my thinking is that no fuses will blow as the fault is in your switchgear itself and not the rest of the loom.

Notes: I do t have an l9 diagram, so you will need to use the l5 diagram and a multimeter and see if your loom is functioning the same way, the below is based on an l5 loom and only uses the LHS main block:

Orange wire, wire this via the switch to the green (left indicator) and grey (right indicator) wires, this is now your indicator switch

Blue/yellow wire, wire this via a switch to the red/yellow (low beam) and red/black (high beam) wires, this is now your selector switch.

Make sure nothing is loose or touching or grounding, and is secure, now go for a ride as normal, if the fuses still blow then it's a fault further downstream, if the fuses don't blow then your issue is grounding out through the LHS switchgear
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003

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