SOHC.co.uk Forums > CB750
Wiring problem
sprinta:
--- Quote from: Lobo on June 15, 2018, 05:18:10 AM ---Hi again Andy,
Attached a modified circuit diagram as to how my K2 was wired, iaw the UK additional LH Main switch and its external wiring (ugh). I read that it was incorporated to stop you plunging yourself into total darkness as you went from HI to LO Beam... and thence inadvertently to P (= actually OFF). Aargh..
(still bloody useless as you were left with a wee park lamp ...)
So... this add-on UK switch ADDITIONALLY connects the BLACK Ignition supply to the BROWN/WHITE Inst illum lamp circuit ... ie see the attached diagram, noting that switch terminals TL & IG are effectively connected when this UK switch is ON.
The ‘UK’ switch then controlled power to the Park / Tail lamps via the Inst Illum circuit with the IGN Switch in the P1 position.
So... with the Ignition Switch in P1
(1) UK switch OFF ... P= no lights at all, L=LO+Park+Tail+Inst, H=HI+Park+Tail+Insts
(2) UK switch ON..... P=Park lamp+Tail+Insts; L=LO+Park+Tail+Inst, H=HI+Park+Tail+Insts
With the Ignition Switch in P2..
(1) The above BLACK feed / Inst BROWN/WHITE circuits not energised, and the tail / park lamps now get their power from the perm live RED.
Personally, I hate the crappy UK Switch and it’s external wiring, and so have deleted it. The choice was to return to the ‘standard’ Honda wiring & occasionally plunge yourself into complete darkness... or instead, splice the BLACK directly into the BROWN / WHITE.
I’ve gone for the latter... the downside being that the lights come ON immediately with ignition P1, ie behave as in (2) above.
Just a final comment on the typical wiring diagrams... such as I’ve attached. The diagram show 4 different RH light switch selections, ie P (OFF), H (HI Beam), Neutral (switch some mid position) and L (Low Beam). You have to read them in isolation... ie one switch position at a time.
SINCERE apologies if I’m teaching you to suck eggs here... 😳!
(1) the LIGHTING DIMMER SWITCH OFF box shows the switch in the P position, no connections are made, everything is actually OFF. Dead. Nada.
(2) the next box down, ‘HIGH’ illustrates the switch internal connections with H selected, ie the IG (ignition) is connected to TL (tail light) and also HB (High Beam)
(3) the next box down, ‘NEUTRAL’ shows the switch in some neutral / mid position, and shows all connnections are made / lighting is safe. (Ie IG connected to TL, and HB, and LB (Low Beam)
(4) the lowermost box ‘LOW’ shows the switch internal connections with L selected. (Ie IG connected to TL and LB)
Read the COMBINATION Switch in the same way... (to you & me it’s the Ignition Switch with its 3 positions, OFF, P1 (Ignition ON) .... & P2 (Park)
Hope this helps.. in my modified wiring diagram I’ve shown the front Park / pilot lamp wiring in blue.. (should be BROWN)...limitations of my iPad alas.
Cheers and good luck, again, accept my apologies if boring you with the obvious.
Simon
PS - Andy, I’m not saying this is how a 1973 K2 was out the Dealership.... I’m rather saying how mine was wired when I became its ‘next minder’ it in 2012.
--- End quote ---
Thanks Simon
Will digest and have a good go over the weekend to see if I can try and better understand the circuits and sort the problem?
However, I do note that I have also encountered the Neutral light becoming intermittent so there may well be a link there?
Andy
sprinta:
--- Quote from: K2-K6 on June 15, 2018, 09:03:37 AM ---Have you verified that the ignition switch making all of the contacts it should do?
http://www.sohc.co.uk/index.php/topic,16187.0.html
We were talking about it on the above thread recently and could assist if you meter the switch through, especially as you're using a new loom.
--- End quote ---
Thanks for the reply and link.
Since when I got the bike it came with seperate ign and seat keys and no key for the steering lock I replaced them all with a new Honda lock set. The ign has the earlier round connector and I don't believe that as new should have any contact problems and as indicated the lights had been fully working but for some reason the pilot and rear light have ceased working in both the P1 and P2 ign positions.
Andy
hairygit:
I assume you've checked the sidelight and tail light bulbs are actually okay and not blown, and the bulb holders are clean and corrosion free? (stranger things have happened)
Lobo:
Ha! hairygit - good point. Eggs on faces all ‘round if you’re right. Sprinta, for gawds sake don’t admit to it if bulbs blown etc!
mickwinf:
I had a similar problem on my 550, turned out to be the ignition switch, also do you have a separate fuse for the side lights?
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