Earthing light bar

[listerjp2]

Hi all

I have a chrome light bar which the headlights and indicators fix to.

Both the headlights and the indicators are earthed through the bolts which attach them.

My question is can I just earth the bar thus saving four earth's back to chassis?

Had a look on the tinternet but can't find anything.

Adrian

[stevejgreen]

Re: Earthing light bar

Unconventional but nothing to stop you from doing just that. But the single earth cable must be of sufficient capacity to carry the combined load of all side, dipped, main beam, and any other lighting attached to the bar plus a safety factor.
What did you decide to do about your headlamp switch rated at 5A?
If you use a remote relay box, you can run a similarly large fused cable from the battery, and then much smaller cables from the switch to power only the relays.

[listerjp2]

Re: Earthing light bar

Unconventional but nothing to stop you from doing just that. But the single earth cable must be of sufficient capacity to carry the combined load of all side, dipped, main beam, and any other lighting attached to the bar plus a safety factor.
What did you decide to do about your headlamp switch rated at 5A?
If you use a remote relay box, you can run a similarly large fused cable from the battery, and then much smaller cables from the switch to power only the relays.

Bought new headlamp switch from CBS correctly rated.

Also now have relays for windscreen/wash wipe, heater, indicators/hazard, dipped beam, main beam.

Along with a remote relay box and a suitably rated fuse for the live feed to relay box.

All cables where required, are rated for 30 amps.

As far as earth for the bar, I was looking at battery rated cable.

Adrian

[Mike]

Re: Earthing light bar

Hi all

I have a chrome light bar which the headlights and indicators fix to.

Both the headlights and the indicators are earthed through the bolts which attach them.

My question is can I just earth the bar thus saving four earth's back to chassis?

Had a look on the tinternet but can't find anything.

Adrian

Hi Adrian

In theory this works, but in practice there are some serious issues you might wish to consider!

Taking the cables back to an earth in the loom is the safest set up. It is unlikely all the earths would fail at the same time.
If you choose to run all your earths through the light bar, you create the risk, however small, that over time the single contact earth fails due to corrosion/poor contact and you have the potential to lose ALL your lights together- potentially very dangerous if it happens whilst driving at night!!
For long term reliability I would take your earth cables back to your loom and right back to the battery, rather than to the chassis.

For neatness you can take the cable back into the headlamp bar, and out through the triangle plates so they are not exposed, and hidden from view.



How close are you to having your Roadster on the road?

Mike

[listerjp2]

Re: Earthing light bar

Very close, I am doing a car sos and want to complete by Sunday 3rd July.

If not I will be going to classic le mans by eurobox.

Nothing like a deadline to concentrate the mind.

Adrian

[stevejgreen]

Re: Earthing light bar

Mike has a point, but given that Marinas generally have a single fuse to the lighting system, the same could be said, total lighting failure is always possible.
Starter motor cable usually spec'd for 150 Amps or more is a bit excessive for a load that should be, four approx 60W bulbs, giving a total of 20Amps.
I assume if you are reworking a loom, that you will try to maintain the BS-AU7 colour codes for the new wires. If nothing else to make it easier for the next owner.

[listerjp2]

Re: Earthing light bar

Mike has a point, but given that Marinas generally have a single fuse to the lighting system, the same could be said, total lighting failure is always possible.
Starter motor cable usually spec'd for 150 Amps or more is a bit excessive for a load that should be, four approx 60W bulbs, giving a total of 20Amps.
I assume if you are reworking a loom, that you will try to maintain the BS-AU7 colour codes for the new wires. If nothing else to make it easier for the next owner.

I have decided to use 30 amp cable and the bs-au7 colour codes.

It's a new loom meeting the standards above.

It would be silly not to use the same colour codes

Adrian

[listerjp2]

Re: Earthing light bar

Hi Adrian

In theory this works, but in practice there are some serious issues you might wish to consider!

Taking the cables back to an earth in the loom is the safest set up. It is unlikely all the earths would fail at the same time.
If you choose to run all your earths through the light bar, you create the risk, however small, that over time the single contact earth fails due to corrosion/poor contact and you have the potential to lose ALL your lights together- potentially very dangerous if it happens whilst driving at night!!
For long term reliability I would take your earth cables back to your loom and right back to the battery, rather than to the chassis.

For neatness you can take the cable back into the headlamp bar, and out through the triangle plates so they are not exposed, and hidden from view.



How close are you to having your Roadster on the road?

Mike

Hi Mike


I take your point but I will stick with my plan, albeit with some risk attached.

Thanks for the picture, exactly what I have just done.

I remember with my previous marlin, it had a cable from the lights running through the suspension cover, always thought it looked naff.

Adrian

[andyf]

Re: Earthing light bar

FYI mines all earthed through the inner wings to the chassis.

[stevejgreen]

Re: Earthing light bar

I have decided to use 30 amp cable and the bs-au7 colour codes.

It's a new loom meeting the standards above.

It would be silly not to use the same colour codes

Adrian

I am pretty certain that the Marina lighting circuit fuse was 35A. no point in reducing cable size down to 30A, it's not a significant change in diameter or cost. I would go for 40A.

[listerjp2]

Re: Earthing light bar

I am pretty certain that the Marina lighting circuit fuse was 35A. no point in reducing cable size down to 30A, it's not a significant change in diameter or cost. I would go for 40A.

No hassle I have both.

Adrian