Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: ted_paper on April 09, 2015, 05:42:12 AM
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Hi
The neutral indicator light on my 400 has suddenly stopped working - the rest of the lights in the console are OK. I've changed the bulb but that is the extent of my electrical skills .
Any guidance on where/what/how to check next would be appreciated.
Thanks
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Ted go to the oil pressure switch, remove the wire and ground it to earth, light should come on.
If it does you need to look at the switch, if not look at all the connections.
Did you clean up the contacts on the bulb when you replaced it.
Regards,
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I think Paul means the neutral switch not the oil switch
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How the bulb works is....It's supplied with 12v from the loom and the neutral switch supplies the 0V (when in neutral) to complete the circuit.
If the oil pressure lamp works, we can rule out the 12v side because it's works the same way.
This leaves the switch and the loom.
If you get a length of wire, attach one end to battery negative and use the other end to earth the neutral switch wire. That should make the bulb light 💡 up.
The wire you're looking for is green with a red stripe.
Let me know how you get on.
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Ted,
Further to the above it might be a bad loom plug.... it's that big plug behind the battery with yellows, red, green.... and the oil px / neutral switch feeds. If all else fails give this a check / clean.
Whilst it's apart, and as Paul & Mike suggested, stick a jumper wire into the red-green (upper connector) and the other end to any good earth... and the light should illum. (ignition on / bike in any gear)
Simon.
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Oops :o I did mean the neutral switch.
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Thanks guys,
I'll check it out this weekend and let you know how I got on.
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My neutral light also stopped working and from a search I found this thread.
Having got access to the switch I find that if I connect the cable to earth the bulb lights.
This sounds as if the problem is with the switch.
I have a couple of old switches from a box of parts but don't know if they are working.
Can anyone tell me where to check for continuity between? Obviously the terminal where the wire connects, but where else?
Alternatively has anyone got a spare working switch they would be happy to let go of?
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My neutral light also stopped working and from a search I found this thread.
Having got access to the switch I find that if I connect the cable to earth the bulb lights.
This sounds as if the problem is with the switch.
I have a couple of old switches from a box of parts but don't know if they are working.
Can anyone tell me where to check for continuity between? Obviously the terminal where the wire connects, but where else?
Alternatively has anyone got a spare working switch they would be happy to let go of?
The switch is grounded at one side
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Its a short circuit between the wire and the body of the switch when in neutral
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That was the query, the body of the switch is plastic. There is a metal cap at the 'plunger' end but I don't
think that is intended to contact with any part of the crankcase; electrically it is not connected to anywhere else.
I played around with the switches I had and found one that seems to work. The short circuit is between the
metal 'plunger' and the terminal. There is a raised area on the gear selector that depresses the plunger when
in neutral, closes the circuit and the neutral light comes on. It seems a slightly strange to me, using gearbox
components as part of the circuit, but obviously works (as long as the switch is OK).
I fitted that switch and the neutral light now works as it should. However I still need another switch as the one
that worked came from a G5 engine I have on the bench which now does not have a working neutral switch.
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you are right the spring loaded contact comes into contact with something inside the gearbox possibly. manual is very vague on it and last time I stripped one of those engines was in 1986. On the twins its an oval shaped bit of plastic with a brass section moulded into it but can't remember on the 400F. On the 250/350 twins the switch is open to all of the chain flung grease etc as it's in the transmission cover, so actually a better (slightly) design on the 400/4
My copy of Honda shop manual is here BTW
https://www.dropbox.com/s/zh31qynxfimw8pb/400_4%20Shop%20Manual.pdf?dl=0
[attachimg=1]
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Thanks Ash.
Yes, the switch comes into contact with what looks like half a ball bearing on the selector drum.
You can see this down the hole for the switch but I can't get a decent photo of it.
On the G5 twins the switch is also in the transmission cover with just a metal guard to keep the worst of the grease and muck off.
Can't be that bad an arrangement though - that is the switch that worked!