S

Skelo

Member
wiring that has me a little stumped.

I want it to come on, when the full beam is activated.

I've bought a wiring harness, which comes built in with a relay and a switch. The switch has 3 wires, one of them is white, which I believe is the trigger wire.
https://www.ebay.co.uk/itm/325270007085?mk...media=COPY

Since taking the photo, I've discovered i can't put it there, due to what looks like the cruise control radar sensor being there, so will fit it below the number plate.
20241202_145921.jpg


With that in mind, I plan to not use the switch, but use the trigger wire, to splice into the full beam wiring of the headlight, so it comes on at the same time the full beam comes on.

Which wire is for the full beam?

I can find an earth point easy enough (lots of bolts to attach the earth wire from the harness to), is the live wire to the jump point (in the engine bay), bolted to the underside of the stud, so I can then bolt the live from the wiring harness to it?

Any help will be greatly appreciated
 
Skelo said:
wiring that has me a little stumped.

I want it to come on, when the full beam is activated.

I've bought a wiring harness, which comes built in with a relay and a switch. The switch has 3 wires, one of them is white, which I believe is the trigger wire.
https://www.ebay.co.uk/itm/325270007085?mk...media=COPY

Since taking the photo, I've discovered i can't put it there, due to what looks like the cruise control radar sensor being there, so will fit it below the number plate.
View attachment 331316

With that in mind, I plan to not use the switch, but use the trigger wire, to splice into the full beam wiring of the headlight, so it comes on at the same time the full beam comes on.

Which wire is for the full beam?

I can find an earth point easy enough (lots of bolts to attach the earth wire from the harness to), is the live wire to the jump point (in the engine bay), bolted to the underside of the stud, so I can then bolt the live from the wiring harness to it?

Any help will be greatly appreciated
Click to expand...
As far as I'm aware, that low level light would be illegal coming on with the headlight main beam.
A relay is essential to provide the power needed.
 
Datatek said:
As far as I'm aware, that low level light would be illegal coming on with the headlight main beam.
A relay is essential to provide the power needed.
Click to expand...
Aux mainbeam lights are not illegal, but they should have a way of disabling them in theory....
 
I will be using the wiring harness that I have listed, thus having a relay and a fuse on it.

The light won't be that low (as in the picture i put up), but will positioned under the number plate.
Out of interest, why would it be deemed illegal tho?
 
Skelo said:
I will be using the wiring harness that I have listed, thus having a relay and a fuse on it.

The light won't be that low (as in the picture i put up), but will positioned under the number plate.
Out of interest, why would it be deemed illegal tho?
Click to expand...
Construction and use regulations specify the minimum height of main beam lights or at least they did. There is also a maximum wattage. What you plan if you leave out the switch could well be an MOT failure.
 
Skelo said:
wiring that has me a little stumped.

I want it to come on, when the full beam is activated.

I've bought a wiring harness, which comes built in with a relay and a switch. The switch has 3 wires, one of them is white, which I believe is the trigger wire.
https://www.ebay.co.uk/itm/325270007085?mk...media=COPY

Since taking the photo, I've discovered i can't put it there, due to what looks like the cruise control radar sensor being there, so will fit it below the number plate.

With that in mind, I plan to not use the switch, but use the trigger wire, to splice into the full beam wiring of the headlight, so it comes on at the same time the full beam comes on.

Which wire is for the full beam?

I can find an earth point easy enough (lots of bolts to attach the earth wire from the harness to), is the live wire to the jump point (in the engine bay), bolted to the underside of the stud, so I can then bolt the live from the wiring harness to it?

Any help will be greatly appreciated
Click to expand...
Most modern cars are not designed to fit things like light bars, good luck physically fitting it.

The wiring is mostly simple for the lightbar, if you want to wire it into the mainbeam, you'll need to start pulling wires and maybe taking things apart. A wiring diagram will help. Do remember modern cars are CANbus, so not as simple as wiring in on an older vehicle.

A local auto-electrician should charge under the cost of a tank of fuel to do this for you.

I would highly advise having a switch to disable the lightbar, if you have bought a decent one, there will be times when you'll want mainbeam without it, as it will reflect too much off signs and things.

In my car (Jimny), I wired directly to the battery and got a matching switch for one of the dash blanks. The Jimny has autolights and mainbeam, so you leave the car to do mainbeam on/off and you can manually toggle the lightbar as needed.
 
You need a 'disable' switch to comply with construction & use regs, as the lighting won't be compliant, i.e. it's for 'off road' use only. you could get a compliance notice from a roadside VOSA inspection, or an MoT fail from a tester that gives a sh!t.
Having it that low will not give you the additional lighting you want, it'll skim along the road surface just in front of the car, reflecting most of the light back at you, making vision poorer rather than better. Connect the existing high beam to terminal 86 of the relay, run terminal 85 inside the car to a switch and connect the other side of the switch to ground. Terminal 30 goes to battery +ve via a fuse and terminal 87 goes to the positive connection of your light bar.

Here's one I fitted earlier....
IMG_20240210_123638_lmc_8.4.jpg



Later replaced with a better quality but straight one (which appears ro be concave when fitted) as the shonky Chinesium LED's are lower output than claimed and the reflectors are 'not great'.
IMG_20240915_122305.jpg
 
Last edited:
300bhp/ton said:
.... Do remember modern cars are CANbus, so not as simple as wiring in on an older vehicle.

...

I would highly advise having a switch to disable the lightbar, if you have bought a decent one, there will be times when you'll want mainbeam without it, as it will reflect too much off signs and things.
Click to expand...
CAN bus has no bearing upon lighting, there are lamp failure monitors on the output circuits but nothing as such to do with CAN - and 'tapping into' a final circuit to trigger a relay won't cause any erroneous messages on the dash.
A lot of aftermarket lamps are marketed as 'CANbus compatible' which makes no sense, what they are is 'lamp failure monitoring compatible', generally by drawing enough current via a shunt to keep the monitoring happy.

I have fitted lightbars to a couple of L405's and yes, switches are both needed to comply with legislation and useful for when there is 'too much light'.
 
Bonnet release cable grommet if you want to bodge it, grommet behind the fuse box under the scuttle (a couple of unused cable sleeves moulded into it) if you want to do it properly.

I've just checked the part number for the bumper reinforcement, it's the same for the L405 & the L494 which means the forward facing RADAR is in the same location - behind the registration plate, to the right of centre, so if you want to locate it in or behind the grille, there shouldn't be anything in the way.
 
Last edited:
Graculus said:
Bonnet release cable grommet if you want to bodge it, grommet behind the fuse box under the scuttle (a couple of unused cable sleeves moulded into it) if you want to do it properly.

I've just checked the part number for the bumper reinforcement, it's the same for the L405 & the L494 which means the forward facing RADAR is in the same location - behind the registration plate, to the right of centre, so if you want to locate it in or behind the grille, there shouldn't be anything in the way.
Click to expand...
That's brilliant, thankyou so much. 😊
 
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