What size fuse and relays for headlights?

[Josho]

I'm thinking of going to Maplin and getting some relays and fuses to make an uprated loom for the headlights on the van and on the Golf.

What sort of ampage would I need? Thanks.

[Josho]

Seen a guide 20AMP fuses.

Do that. I'm going to buy 4 relays I think and a few meters of wire.

That's one relay per light for high and low.

My idea is to take the stock headlight wires out of the bulb holder and put them to the relay.

Off to Maplin methinks.

[Josho]

Oh, one question, ground, to battery or chassis, what's best?

[rubjonny]

id go battery

[Josho]

Sweet. Now ordering all parts off eBay as I can't find my card. It's all in my account.
Cheers Jonny! 

[Josho]

OK, my plan is:

10AWG from battery to project box that contains two relays. One for high one for low. Then take the harness out of left headlight, and use the high and low power cables to trigger the relays.

Then from the relay straight to a distribution block of some kind, still 10 or 12 AWG then distributed to 12AWG for both headlights, running above the radiator, to the right headlight.

Then grounding them to the battery.

See if it makes a difference, put it on the drive front ways to take comparison photos.

[Teutonic_Tamer]

I'm thinking of going to Maplin and getting some relays and fuses to make an uprated loom for the headlights on the van and on the Golf.

What sort of ampage would I need? Thanks.

That would depend on what wattage bulbs you will be using.  If you want to use the rally spec 160 watt bulbs, then they will need a bigger fuse, ideally a remote relay, and some larger diameter wire.

[Josho]

I'm thinking of going to Maplin and getting some relays and fuses to make an uprated loom for the headlights on the van and on the Golf.

What sort of ampage would I need? Thanks.

That would depend on what wattage bulbs you will be using.  If you want to use the rally spec 160 watt bulbs, then they will need a bigger fuse, ideally a remote relay, and some larger diameter wire.

Standard bulbs. No higher then 60W, keeping it legal.

[Ben Lessani]

If you're running 60w - then its 60/12 = 5A, if its one wire for both sides, then 10A - allow some overhead 15A total.

For about a 6ft max length of wire, you're looking at 18 AWG @ 12V.

Personally, I'd ground off the chassis, its a spot neater and the voltage drop will be negliable, esp since its the alternator powering the bulbs, not the battery. Get some extra bits here

More here

[Teutonic_Tamer]

I suppose if the OP is keeping everything standard, why the need for rewiring then? 

Oh, and on cars earlier than a certain age, 100 watt bulbs are actully road legal too.    And I have never been stopped when running 130w or 160w on some older cars I used to own - and I think you may also find that cop cars use very high wattage headlamp bulbs too.