Hey guys,
I recently bought a Lucas Headlight (Lucas 7" H4 Headlamp Unit with Pilot RH) with a Lucas bulb (Lucas P43T Halogen Headlight Bulb 12V) thinking it would be plug and play. However I didn't buy a Pilot bulb nor do I know what one is. This meant only the flash works when I plug the bulb in and none of the other headlight switches work (Or is it a wire fault?). So what is a pilot bulb and how to I wire one up? (I'm going to buy a Lucas Pilot Light Bulb 12V)

Picture is an example of what I bought:



Thanks
DBRMN

The 'pilot' bulb I presume is just a parking light bulb.

The standard K headlight is H4 and the plug connector is already on your loom for both the H4 headlight and the parking light bulb. The parking light bulb also has its own little bulb holder which is a twist and click fit into the original K bike headlight unit. So it should be plug and play as you say. Lack of light in the H4 bulb suggests no high and low power supply is coming through. The earth for the headlight bulb goes back to the loom, its not earthed through the headlight unit.

Ignition on and lights on the right hand side turned on you should have high and low beam functions. Check the connections of the right hand switch gear to the loom.....and also check ignition on is giving you power.

Oh ok so Pilot bulb isn't critical but I should get one. So you think its something in my wiring loom thats what I suspected, it's definitely getting power otherwise the 'flash' wouldn't work. The headlight came with a replacement plug so I think I'm going to solder that in instead and check if thats the problem. Thanks for your reply!

I've actually decided since I've still got the OEM headlight unit I'm going to plug that in and test it just to check before I start hacking the wiring loop apart lol.

The K plug will be the same, H4 bulbs all take same plug so no need to change it.....the bulb should light up if you just plug it into the plug and power up the switches etc. Be wary of touching the bulb glass though, halogen bulbs dont like hot spots so make sure to keep glass clean.

92KK 84WW Olaf wrote:The K plug will be the same, H4 bulbs all take same plug so no need to change it.....the bulb should light up if you just plug it into the plug and power up the switches etc. Be wary of touching the bulb glass though, halogen bulbs dont like hot spots so make sure to keep glass clean.

It just still confuses me why the left hand flash works but the right side on and high beams doesn't?

Separate and different power supplies. The switch gear is connected to the loom under the tank and you may have loose connection there. No power getting through via the headlight switch. Does indicator cancel and right hand indicator work ok? I don't know if they even go through the same fuse or not.

There are interactive wiring diagrams on the portal page, worth a look.

A pilot light is not a requirement under UK law - it hasn't been since 1983. However, that light unit is fitted with one - it's the small (4watt) bulb and fits in the bulb holder that's held in the rubber grommet. Connect the slate/white wire to the centre terminal and a brown wire to the body (earth) terminal. 

And definately keep your fingers off the glass envelope when it's lit up. It's actually quartz and hits a nice balmy 900 degC.

Your school lesson for today : you don't have grey wires, you have slate ones. The reason being is that green has the symbol G or Gr on a wiring diagram, so to prevent confusion with using Gr for grey you have S for slate (as in slate-grey). Similarly, you don't have purple wires because P is taken by pink; you have V for violet ones instead.

92KK 84WW Olaf wrote:Separate and different power supplies. The switch gear is connected to the loom under the tank and you may have loose connection there. No power getting through via the headlight switch. Does indicator cancel and right hand indicator work ok? I don't know if they even go through the same fuse or not.

There are interactive wiring diagrams on the portal page, worth a look.

Yeah all the indicators work as I've just fitted MotoGadget bar end indicators. Ye I think I'm going to need that diagram thanks.

Dai wrote:A pilot light is not a requirement under UK law - it hasn't been since 1983. However, that light unit is fitted with one - it's the small (4watt) bulb and fits in the bulb holder that's held in the rubber grommet. Connect the slate/white wire to the centre terminal and a brown wire to the body (earth) terminal. 

And definately keep your fingers off the glass envelope when it's lit up. It's actually quartz and hits a nice balmy 900 degC.

Your school lesson for today : you don't have grey wires, you have slate ones. The reason being is that green has the symbol G or Gr on a wiring diagram, so to prevent confusion with using Gr for grey you have S for slate (as in slate-grey). Similarly, you don't have purple wires because P is taken by pink; you have V for violet ones instead.

Ok so they're not a necessity perfect. I found a pack of 10 on eBay for £1.57 with free delivery so might as well lol. Ye I've heard about that scary stuff. Thats actually so interesting will definitely help with wiring thanks!

Could it be that the contacts have burned badly in your Hi/Lo switch on your left bar? This is a known problem with K's that haven't had relays fitted to protect those switches.

DBRMN wrote:I've actually decided since I've still got the OEM headlight unit I'm going to plug that in and test it just to check before I start hacking the wiring loop apart lol.

You don't need to hack the OEM harness to add relays. You can add relays and the only "hacking" required would be tapping into the high and low beam wires as relay triggers.

On a side note:  Now you know why Lucas is referred to as The Prince of Darkness.

duck wrote:

DBRMN wrote:I've actually decided since I've still got the OEM headlight unit I'm going to plug that in and test it just to check before I start hacking the wiring loop apart lol.

You don't need to hack the OEM harness to add relays. You can add relays and the only "hacking" required would be tapping into the high and low beam wires as relay triggers.

On a side note:  Now you know why Lucas is referred to as The Prince of Darkness.

I have spade connectors which go into the original K100 loom H4 headlight plug that went on the back of the original bulb. No modifications to wiring.

From there these 3 wires connect to the relay and this is additional wiring, from relay a fused live supply to battery, from relay to the H4 bulb is 3 wires and bulb holder and for this I have a ceramic rather than plastic bulb holder plug, off eBay for about €3 for a pair. Putting relay up near headlight makes sense if its RT/LT fairing to protect it from weather. Ideal is to use same colour wires for the new bulb holder- my bulb holders came with the wires all connected and just left as tails. No switches are needed, its all done through the original switching.


 As it just happens a set of 135dB air horns landed here last week....

So funny thing I've just tried my plugging in my old headlight, and it worked! So I plugged in my new headlight... and it worked! So I honestly have no idea what I did the first time 

duck wrote:

DBRMN wrote:I've actually decided since I've still got the OEM headlight unit I'm going to plug that in and test it just to check before I start hacking the wiring loop apart lol.

You don't need to hack the OEM harness to add relays. You can add relays and the only "hacking" required would be tapping into the high and low beam wires as relay triggers.

On a side note:  Now you know why Lucas is referred to as The Prince of Darkness.

You know what I mean lol. 

Yeah luckily its working for now ahah.