nc35 headlight wiring

[roadrubber]

Hi all,

Just been helping a mate sort out an issue with the headlight wiring on his rvf/nc35 - low beams not coming on.

It seems that the white wire upstream of the connector block where the switchgear wires go into the loom (and through to the headlamps) has a a fault. This was determined by checking voltages on a meter, seeing no low beam when there should have been one (i.e. when ignition is on) and finally seeing the lights come on nicely after bypassing that white wire in the loom with a new one straight to the lamps.

So the problem appears to be well on the way to being sorted but here's my question.

I noticed from the wiring diagrams in the Haynes manual and indeed the setup on the bike, that the headlamps are wired up slightly oddly. Hi beams (blue wire) are same for left and right lamps but low beams (white wire) and ground (green wire) connect to different terminals between right and left lamps. I would have expected the white, green, blue setup to be repeated for left and right and follow the pattern used on the vfr (as shown on the vfr wiring diagram). The different setup means that lo beam setting will power different combinations of filaments between left and right, I think one has both filaments on while the other has just the one. Is that as it should be? What filaments should be lighting for hi/lo and why would the rvf and vfr be different?

Be most grateful if someone could errhh.. shed some light on this for us.

:-)

Cheers,
RR

[Neosophist]

Does it have H4 bulbs in it by any-chance?

Its well documented on here that by putting normal H4's onplace of the standard H4R the extra power will fry the switch-gear and your headlights will stop working.

Fitting a relay for the low-beam is the way to go if you have H4's in there. Chances are something has melted in the switchgear.

[speedy231278]

As above. You might possibly find that if you press down on the top of the hi/lo switch button and or wiggle it about a bit that it works again for a while, but most likely the contacts in the sliding part of the switch have melted their way into the plastic, and become stuck. You can sometimes dig them out, however if you're using 60/55 bulbs then the switch is effectively doomed. And if you can't find one on eBay, it's a special order to Japan, via a Honda dealer and a telephone number price. H4R headlamps in a Honda packet are pretty pricy too.

34901-KY2-702 for the H4Rs, £17.40 each
35200-MR8-900 for the switchgear, £135.43 (no, that's not supposed to be £35.43 although my last one was about that, DSS obviously found a box of unwanted ones lurking in a supply of excess stock!)

[roadrubber]

Thanks for the input chaps. The bike is running with H4's and I realise that needs to be addressed. Even more so thanks to your comments.

That said, I think my description was unclear in the original post, so apologies for that, but the switchgear is not the problem here, it's the white wire in the loom going to the lamps (the switchgear is the first thing that got examined and any issues it might have had have been sorted).

The white wire in the loom has now been bypassed (with the bypass soldered to the white wire coming out of the switchgear and replacing the portion that goes from there onto the lamps. This is doing exactly what it should do (as per the wiring diagram) and everything is lighting up nicely again. The next step is to make the lo-beam switchable (of course, via a relay).

What I'd love to get some insight on is why the lamps are supposed to be wired up as they are on the rvf as compared with the vfr. The difference can be seen by comparing the two diagrams in the Haynes manual if you have that. The vfr uses what I'd have expected to be the only correct way to wire up a pair of hi/lo beam headlamps so the rvf pattern is the mystery to me.

Can anyone share some knowledge on that aspect of this?

Cheers,
RR

[speedy231278]

Do you mean the lack of relay? The UK spec VFR400 had a relay fitted on low beam as being UK spec, it was modified from the Japanese spec because the Japanese market bikes run 60/35W headlamps, whereas in the UK the vast majority of vehicles use 60/55. However, the RVF was never officially imported into the UK, so it is set up to use Japanese spec lamps. The electrical fitting on the back is the same, but the pegs that hold them in place in the headlight assembly are different , probably so you can't accidentally fit the wrong one. The issue is that the switch was chosen that was able to cope with a total of 70W of low beam running through it, and when you fit 60/55Ws, that becomes 110W, or more than a 50% increase in current. So, eventually the extra load damages it.

[roadrubber]

Thanks for sticking with me on this speedy.. again muchly grateful for the insight but also again I don't think I'm quite getting my question across, here's one last attempt. Maybe a picture will help.



The diagrams above show the rvf and vfr headlamp wiring diagrams (note that the j-spec and uk-spec nc-30 would be identical, the only diff being that the grey or white wire going off to the handlebar would be going via a relay much as the light blue wire goes to the hi beam relay).

What I'm curious about is the difference in the connections to the pinouts on the lamps. On the vfr you have blue (hi power), green (ground) then white (lo power) same on both headlamps but on the rvf you have white, green, blue and then green, white, blue. i.e. hi beams same but ground and lo swapped between left and right.

Why is that?

[speedy231278]

It's just a wiring diagram, don't worry about it. Both lamps are wired the same on the bike, or you'd get utterly the wrong result. It will be drawn in the least confusing manner according to the thinking of the person who drew it. I guess in this case they didn't put the white in the middle on the lower lamp to avoid having it cross the green twice. Note that the high beam relay wires are in a different order on the connector too. On one, you have the power on the top two pins, and on the other in the middle. However, in both cases the relay is 2x2 pins, not one line of four, and both the NC30 and 35 use the same part (or can do, the NC30 diagram lists one part number, the NC35 diagram lists that NC30 part number plus another one). So, what order do you draw them in? Likewise, the headlamps have one pin above the other two. Do you draw the top one at the top of the three on the diagram as it's above the other two, or in the middle as the bottom two are outside it when looked at from above?

Just remember the wiring diagram is just a guide. Each part will (hopefully) have the same colour wires going to it, but they might not necessarily be in exactly the same order.

[roadrubber]

Thank you again speedy. You are a lifesaver sir and your patience is much appreciated.

I guess I would have plumbed for the "draw the pins on the bulbs as they appear on the bike looking down from above" option and/or at the very least having picked a pin order for whatever reason do it the same on each bulb but I guess going for the simplest layout of wires is fair enough. I wasn't concerned about the pin ordering on the relay because those are labelled clearly on the bike but again I guess the author of the wiring diagram could be forgiven for assuming that someone rewiring their headlights would know what each of the pins on an H4 or H4R does and hence be capable of "joining the dots".

In this instance, the original connectors are no longer present and whoever wired up the replacements has reproduced a "looking down from above" interpretation of the drawing, this is what made me question my own (somewhat limited) understanding. Thank you so much for putting that straight. I've gained some useful knowledge - about the bike, about lamps and about what's important in a schematic.

Cheers,
RR

[Neosophist]

That doesnt look like the proper wiring diagram from the parts book.

The bulbs are wired the same.

As speedy has said its a crappy drawing.

It seems your bypassing the handlebar switch? In which case it sounds knackered...?

You have classic H4 symptoms without an additional relay installed.

[speedy231278]

Interestingly, the diagram in the Haynes has the lamp pins in a different order!