After riding a stretch of unlit A1 at night the other day and nearly shitting myself in the process I realised my low beams are just pants. This has just been reinforced by riding home in fog so thick I can't see 4 car lenths infront of me.....

So I looked into it and realised that for the price of new H4R bulbs (if I wanted some) I could buy and fit some H4's and the relay to go along with it.

For some reason I couldn't get my head round the wiring this morning so I drew up a diagram of what I thought would work.



Now I'm not sure whether I should replace the bulb connectors while I'm doing this, or if it'd just be unnecessary.

I'm also not sure about the gauge of wire I should use.

I have a 20A relay, a 15A inline fuse, some 14AWG super flexible silicon coated wire, some 17AWG wire on its way, a shed-load of spade connectors and ring terminals, some heat proof sleeving, and two H4 Osram Nightbreaker Plus bulbs.

Will this be enough? And is the wiring in the diagram going to work/be sufficient?

My suggestion:

Relay 87 to headlights in heavy gauge wire

Relay 30 to +ve battery terminal in heavy gauge wire with fuse

Headlights -ve terminal to chassis in heavy gauge wire

Switchgear to relay 85 in light gauge wire

Relay 85 to chassis in light gauge wire.

magg wrote: Switchgear to relay 85 in light gauge wire

Relay 85 to chassis in light gauge wire.

Switch to 86. The NC30 switches on the +ve feed, not -ve.


Oliver, your diagram is correct

Just do as Magg suggests and replace the -ve wires from the bulb holders with something a lot thicker and fit straight to the chassis. Also, there's no need for 14AWG wire to 85 and you don't need to run from the battery, you can use an existing earth (green) on the headlight loom - that wire is only the -ve for the coil and draws no more than a few mA.

So,

T30 wants 14AWG to the battery with a 15A fuse.
T85 can be tapped to an original green earth wire.
T86 is your feed from the switch, 18AWG or 20AWG is fine.
T87 is you load to the lights, you want 14AWG for this.

My typo, as thunderace said 86 to switch.

magg wrote:My typo, as thunderace said 86 to switch.

You got to admit it's silly putting the 5 next to the 6 on the keyboard

Cheers for the replies

Just to clarify, and to get it sorted in my brain, I drew another diagram out. This more what you suggest?



For the earth point can I use the small earth point on the left side of the chassis?
And as written in the diagram can I use the original white wire from the switchgear to relay 86? Or will it need plugging in elsewhere?

Yes that looks fine. You can use the earth tag on the frame and the white wire.

On UK models it's white from the lamp to the relay then White/Black to the switch, it depends on how anal you want to be about it

thunderace wrote:Yes that looks fine. You can use the earth tag on the frame and the white wire.

On UK models it's white from the lamp to the relay then White/Black to the switch, it depends on how anal you want to be about it

Awesome, if it works I don't give a rat's ass about what it is on UK models!

Now just to wait for my H4 adapter plates

Did you get yours from that place in Hungary or some suchlike? You might be wanting a Swiss file as the top tabs were a little oversized on the ones that I got. Only a tiny bit, but enough that they won't fit straight in. They're very cleanly cut though.

Yeah I did, found them from the link you put in another headlight post not that long ago

I have some small files from making airfix kits, so I should be fine.