SOHC.co.uk Forums > CB350/400
Blown fuses
Bryanj:
Dont trust beep, resistance can alter it. Yes a short would be same as touching leads together, you may find different resistances which can lead to an answer. Yes red/black points is every point(connector) you can find e.g. red at both sides fuse(need good fuse fitted for tests but no battery), rectifier connector, in headlamp then same for black not forgeting all the block connectors. Should have said reconnect ign switch and turn on before checking blacks
mattsz:
Something I can actually contribute to! Not sure if it will be helpful, though...
--- Quote from: Nurse Julie on April 04, 2020, 04:19:40 PM ---A question for those of you with USA bikes with the daytime light, does the tail light come on and stay on with that set up?
--- End quote ---
--- Quote from: Bryanj on April 04, 2020, 04:25:35 PM ---Yes it should but via a different circuit, not if UK RH switch has been fitted(lights on/off switch)
--- End quote ---
Brian has it right regarding the USA tail light.
--- Quote from: orcadian on April 04, 2020, 11:09:40 AM ---Hi Mark,
Your bike is a US import which would once have had daytime running lights at the front with twin filament indicators. Have those wires from that system got mixed up with some others, especially earths? Can’t remember the colours of those though.
Ian
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--- Quote from: Oddjob on April 04, 2020, 12:53:59 PM ---Light blue/white and orange/white IIRC
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Something to file away during this process, just in case - Ian is, in theory, correct about the colors, but some USA bikes don't "fully" adhere to those wire color rules - some use black wires for the front turn signals and running lights with small colored bands at each end: plain blue and plain orange for right and left turn signals, and blue/white and orange/white for right and left running lights. For example, the attached pic shows the wiring from my '77 - the top three black wires show the blue/white, orange/white and plain orange bands. You can see how the banded black wires, which lead to the fixtures, connect to the proper colored wires in the harness...
Lobo:
Oggers, as already said, you’ve got to be methodical, and to do this, really need the correct wiring diagram. Yep they can be daunting, but with a beer and a few mins become easier... just think of it as water flowing through pipes and taps (switches!)
Thoughts: and bearing in mind I only have access to a UK Wiring Diagram (attached)
(1) DON’T put a 35A fuse into a 15A rated Circuit. By doing this you are potentially overloading the wiring loom which has a design limit (30A I think?) meaning that you’ll just exacerbate your problems and may melt the loom unnecessarily.
(2) From your diagram note which services the two 7A fuses cover... on the UK bikes it’s (1) the Parking Lamp + speedo / tachometer illuminations and (2) the HI/LO beam supplies. (They are downstream of / supplied by the main 15A fuse). IF neither of the 7A fuses blow at ignition ON you can probably assume these services are not the culprit as the 7A fuses would blow long before the main 15A fuse. This may save you a bit of time.
(3) Basically, the RED from the battery goes via the 15A fuse to your ignition switch. At IGN ON it becomes connected to the BLACK.... which sends power to the various components - easily seen in the wiring diagram. Given what you describe, one of these components is shorting to ground via a misconnection ... or trapped, damaged insulation etc.
(NOTE that you should NEVER see a BLACK - GREEN bullet connection as dark GREEN is always Earth (ground) wires on the old Hondas.
(4) Try disconnecting ALL the BLACK bullets shown downstream of the ignition switch - circled in red on my UK diagram. This will cut power to:
(a) the Neutral / Oil Pressure switches
(b) the Lighting circuit supply (although discussed & ultimately on 7A circuits)
(c) the kill switch supply
(d) the starter motor solenoid
(e) the rear brake switch
(f) the front brake switch.
* ensure all these loose disconnected Black bullets (from the IGN Switch) cannot touch / short any other wires. (If your loom is original you should be ok here as they will be the Female connector with enclosed plastic sleeve)
(5) Now, with a 15A fuse try the ignition ON... if all ok then a fault lies in one of the above circuits.... connect them one at a time to single out the culprit.
(6) If the fuse blows again, the problem lies elsewhere in your circuit / loom. Note from the wiring diagram that there are a couple of ‘hard’ connections... eg the Regulator & Winker Relay. Disconnect these... and turn the IGN ON... if the fuse stays good then your fault lies in one of these...
(7) If after all the above the fuse is still blowing it’s beginning to point to a problem with perhaps the IGN switch itself... or the loom; bad insulation etc. Hope it doesn’t get to this...
Finally, whilst the UK Wiring Diagram is probably pretty accurate, it will have differences and you really need to source the correct one for your bike. Mattsz?
Good luck, ‘tis all a pain to be sure.
Simon
Woodside:
Just a thought as I noticed this the other day ..
Have you had the rear taillight disconnected
It has 2 green wires and on my bike one has the faintest of yellow trace marks....almost invisible especially in a darker garage . One is an earth the other a switch on to
the lamp
I'm assuming this would run to the headlight ....if connected wrong...or together thay would cause this fault
mattsz:
--- Quote from: Lobo on April 05, 2020, 03:44:29 AM ---Finally, whilst the UK Wiring Diagram is probably pretty accurate, it will have differences and you really need to source the correct one for your bike. Mattsz?
--- End quote ---
Here's my original post:
http://www.sohc.co.uk/index.php/topic,17969.msg156361.html#msg156361
You'll find both UK and USA diagrams as attachments, plus a dropbox link to the USA diagram at the bottom. As most of you know, they're very similar, with the exception of the running lights and headlight switch.
Also, here's a dropbox link to a pdf collection of "detail" diagrams which may help - too much time sheltering at home maybe?
https://www.dropbox.com/s/i05w722o7fxjovh/Honda%20CB400F%20USA%20wiring%20diagrams.pdf?dl=0
This link may die sometime in the future, but I'll leave the file there for now...
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