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RD400F electrical problem SOLVED
Posted: Thu Nov 08, 2012 9:18 pm
by tarjla
Bike was running fine then the neutral and oil lights went off,engine still running,also horn and indicators stopped working.Checked fuses,all blown and all connections rusty so swapped them for blade fuses.Fuses still blowing.Checked wires in fuse box with multimeter,the 20 amp connection is live with no keys in the ignition,the other two are not live,should the 20 amp fuse connection be live all the time,cheers
Re: RD400F electrical problem
Posted: Fri Nov 09, 2012 4:39 am
by hybrid
That is probably a direct battery feed, so no problem there.
Checking whether things are live or not is not what you're looking for. You've obviously got a short to earth somewhere if you're blowing fuses straight away. Could be a pinched wire somewhere.
Blowing every fuse on the bike though.... that's weird. Do they blow as soon as plugged in, or after you turn on the ignition, or after you start the bike?
Re: RD400F electrical problem
Posted: Fri Nov 09, 2012 5:43 am
by EPApolice
Your bike should not run if the main fuse was blown because this cuts the power to the ignition. Sounds like someone has done a few good bodges on this bike before selling it. Get yourself a multimeter and start checking. The loom may have melted. If you need one I have a few spare.
Re: RD400F electrical problem
Posted: Sat Nov 10, 2012 12:01 am
by tarjla
Thanks for replying.The 20 amp fuse blows as soon as I turn on the ignition,the others blew when I tried the indicaters and lights.The wiring has been tampered with but everything was good until a day after changing the cracked neutral switch cover for a yambits one.How can you tell if the loom has 'melted'
Re: RD400F electrical problem
Posted: Sat Nov 10, 2012 7:20 am
by EPApolice
The only way to check the loom is to pull back all the insulation. Sometimes if you get a dead short the red gets so hot it melts on to the other wires around it and then your screwed.
If I was you I would open the head hight and disconnect the main loom in there and check the wires with a multi meter. I would start with the ignition switch. Its not uncommon to find the earlier models switch gear used on the later bikes. The wiring is different in some items and also you get a few wires going to different colour wires. So a blue may go to a grey or something like that. I'm afriad to say there are no short cuts here so you really have to just sit down and check everything one by one and get yourself a wiring diagram, there should be one on the aircooled site to download.
Re: RD400F electrical problem
Posted: Sat Nov 10, 2012 2:07 pm
by tarjla
Update,the 20A doesn't blow any more but every time I turn on the ignition the bottom10A brown wire fuse,I think for the indicators,blows.If I turn the key further the lights come on okay.When I turn on the ignition neither the neutral or oil lights come on,the bulbs seem okay,cheers
Re: RD400F electrical problem
Posted: Sun Nov 11, 2012 4:42 pm
by tarjla
Checked the wiring today with mulimeter took each item connected to loom off one by one.Even disconnected whole loom and checked,found nothing,put back together,still blowing the fuse,any ideas,cheers

Re: RD400F electrical problem
Posted: Sun Nov 11, 2012 6:23 pm
by EPApolice
Check the loom for continuity. With the loom completly disconnected and the fuse in the red circuit in place put one end on the battery end and the other on the headlight end of e red wire. Then keep the battery end in place on the red wire and check every other wire in the loom at the headlight end. If there is a short in the loom another wire will also give a reading. Make sure the whole loom is disconnected first including the battery.
I read on the AC forum that you found the red soldered to the brown was that the case.
Re: RD400F electrical problem
Posted: Sun Nov 11, 2012 6:57 pm
by tarjla
I had a red wire coming into the 10A brown circuit fuse box,when I pulled back the insulation I found someone had soldered a piece of red wire onto the brown one to lengthen it,nothing to do with the red ignition circuit.I have put the loom back on the bike so will take it back off during the week and give your info a try,cheers
Re: RD400F electrical problem
Posted: Mon Nov 12, 2012 5:39 am
by hybrid
You could also disconnect the positive wire from the battery, turn your ignition switch to the on position or where ever it needs to be to blow the fuse. Then check ohms between ground and the fuse that keeps blowing to see if you have a short.
Also unplug everything that is powered from that circuit - instrument cluster, indicators etc. If you measure nothing to ground while all the stuff is unplugged then your loom is OK. Plug each item back in one at a time and measure from fuse terminals to ground each time. You'll need to remove the globes from any lights in that circuit, or you'll get a reading to ground through the filaments.
Re: RD400F electrical problem SOLVED!!!
Posted: Sun Nov 18, 2012 9:18 pm
by tarjla
Thanks for the help guys,finally found the problem,a faulty flasher cancel unit.The unit had an intermittent fault in one of the wires.Luckily indicators will work without it as not available new anymore