The light switch and horn / flash switch on my 78 T3 finally feel apart so I ordered a new Domino switch from Gutsibits allong with a new 12 way connector housing and pins. Although it comes with a diagram I can’t work out where the new wires go in this block. The rest of the wiring is standard.
Anyone fitted one of these switches before and can give me some help?
Thanks
Rich
Hi Rick
If you test the various wires from the switch with a multimeter or a battery and bulb so you know what they all do I can send you a coloured wiring diagram so you will see where they all go and advise you if you can’t. 
Hi Chris
I got a drawing from Gutsibits with the switch and I’ve attached that along with the original bike wiring diagram. The original switch has 10 wires going into the 12 way connector but the new switch only has 9 so I guess there is one less +ve feed for the lights. Also I think the original switch is earthed through the handlebars /frame but the new one isn’t.
I’ve tried to work it out but drawn a blank so any help you can give will be great.
Many thanks
Rich
?
think my files are too big to load so I’ll try again
Hi Chris
Looks like I can’t get enough resolution with the file size restriction for the forum. Can I send you an email direct?
Rich
Hi Rich
PM sent, starting with the indicators
Function ------------ New Domino switch ---------- Original loom
Indicator feed ------- Blue/Black ---------------- Orange
Left turn -------------- Blue ------------ Green/Black
Right turn ------------ Red ------------ Pink
Lights (on original the red/black feed is live with ignition off, but Domino appears not to allow for this as there seems to be no separate feed for the parking lights)
Lights feed ------------ Green ------------ Red
Park lights feed -------- Not applicable ------------ Red/black
Tail light and clocks – Yellow ------------ Yellow
Dip headlight ------------ Black ------------ Green
Main headlight ------------ White ------------ Brown
Horns (on original the horns are earthed by the switch, it looks like the domino switch supplies power to the horns, if this is the case you will have to disconnect the existing feed to the horns and change this to a permanent earth wire, may need swapping over on the horn itself to make it work)
Horns feed ------------ Green ------------ Black
Horn ------------ Grey ------------ N/A as switch is earthed
Passing flash (as with the horn switch this may need a little more thought as the existing switch earths the flash relay and the new domino switch connects two wires green feed and black/white. As with the horn you could use the black/white wire from the switch to feed the flash relay, but you would need to ensure that it connects only to the coil feed and not the load as well otherwise the relay would not isolate the switch from the high load required by the headlight. I have also added a further two relays to my own bike, one for the headlamp on/off and one for main/dip, these remove all high load from the handlebar switch, (I guess these new switches will be ok with high loads though.)
Flash feed ------------ Green ------------ Grey
Flash ------------ Black/white ------------ N/A as switch is earthed
I hope this helps
Thanks Chris your help is much appreciated and you confirm a few things I thought already (esp horn/ flash function earthing).
I’ll tackle this next weekend and post how it goes.
Great wiring diagram by the way! Why couldn’t Guzzi have done something similar themselves (although I remember things were a bit more monochrome in the 70s).
What a great bunch Guzzi people are
Rich
Yes I was going to say, don’t forget T3 OEM switch will have separate circuit for the side/park lights so that they will work in ‘park’ position of ignition switch, but nothing else will.
Had this when I wanted to use Honda switches, got quite complicated, had to add a relay to prevent headlamp being turned on in ‘park’ mode.
Simplest answer is only have the ‘side’ lights work when ignition is on. But not for ‘park’. 
There is only one power feed to the whole switch cluster, so there is no other option than park lights (side lights is a car term) to be on when the ignition is on. Any alternative would mean taking the switch apart, isolating the park light contacts and running a separate feed from the headlamp live feed, even then it would be difficult to isolate one live feed from the other.
I do not believe that it would be easy at all to use a relay as Mike H suggested to disable the headlamp when the parking lights are on. The tail light and clocks lamps are on the park light circuit on a T3. As the switch cluster has only one live feed the ignition will be on with the parking lights, so will the horns, indicators and headlamp (also on the same feed) all be live so the new relay wiring would have to take all of those into account too. I think this solution is a dead end street.
What is the point of having parking lights anyway? How often do you park your bike so badly that you have to put parking lights on? My suggestion is wire them as I note above and if an MOT tester wants to see parking lights, turn the ignition on and show them to him, then turn them off.
Yes would be easier.
I remembered, the Honda switches I had were lighting switch on the right, dip switch on the left, which is not what we have here. So my method of using a relay wouldn’t be possible.
Rich, as I said before the relay route appears to be a dead end street 
Hello
Finally got round to this job and got everything working as follows
Even without ignition on all lights work (park, dip and main) including tail light and instrument lights. Also horn works without ignition on.
Brake light and indicators only work when ignition is on - ok. Also switching on ignition lights up oil, neutral and gen idiot lights as it should.
The original switch connected the horn to earth with a live feed to the other side of horn. So I just disconnected that feed, connected a permanent earth to the horn (via earth point at top of cam chain cover) and the horn switch wire is now the new feed to the horn.
Flash function still needs sorting. Because of the internal way the flash relay coil is wired I can’t use the relay with a positive feed from the switch. So for now I’ll connect the switch direct to the dip beam and bypass the relay as the switch should be ok for intermittent use (40W = 3.3A). Over winter I’ll fit a new relay for this function and some more for the other light functions as suggested already.
In summary all works as it should even parking light which should please the MOT man (although bike will be 40 this year so MOT will be a thing of the past) and I never use parking lights anyway? As long as nobody knocks on my lights by accident (or on purpose) while parked and drains the battery then we’re good to go and I’ll run it like this for now.
Thanks for all your help and for anyone else in future I’m attaching a small chart with all connections on.
Richard
Well done Rich
My only comment is that if you had connected the live feed to the switch from red/black and not the red wire then every function on the switch would only be on when the ignition is on. This is probably not a problem for you unless you park the bike up somewhere and a chav starts playing with the switches. I can now see that in my post above I got the red and the red/black the wrong way round, sorry. I hope it is not too much problem to swap these.
Regards Chris
Early Meriden 750 Triumphs were like this. Lighting switch was a big black toggle bang in the middle of the (chrome) headlamp shell just BEGGING for someone to push it over. Can’t remember if I had it done to me though but wouldn’t be surprised.
Thanks for the final tip Chris.
Today I switched the green wire over to pin 1 instead of pin 4 like you suggest and everything now only works with the ignition on. Luckily I bought a Molex pin extracting tool for just this reason as I expected to get it wrong a few times!
Of course the parking light now doesn’t work with ignition off but will argue that with the MOT man if I have to!
Next job is to replace the right hand switch where the old switch was also earthed through the body to the handlebars. The new Domino one isn’t so I guess I’ll have the same problem of the polarity at the starter relay (although the kill function is easy to work out). Should be straightforward though but I’ll let you know how that goes when I get round to it but for now the weathers getting better so I’d rather ride it…
Rich
Rich
Let us know what switch you get and if you get a wiring diagram let us know and we can give you even more useful help and advice! 