Headlight earth question.

Garp · Post by **Garp** » Sat Feb 11, 17 7:37 pm

Hi again all.
Spent a small while today removing old sealed beam units from the Challenger.
Tracked the wires back and have confirmed the original loom colours are present and correct - violet for dipped and red for high beam.
I'm going to splice in the two relays as per the very handy drawing from a fellow member I found here (thanks a lot, simple and easy is best and your drawing is both)
I'm hoping to lose the old connectors and just add in the new connectors at the appropriate place, as per the illustration.
Can I ask, can I just use the exiting black wires as a default earth - it was with the sealed beams but the drawing indicates each bulb having a separate earth - is this necessary to separate them because they are now halogens running from relays?
I could of course run a whole new set of cable for the lot but cannot see why I shouldn't just be able to use what is here.
Simple enough question I know but sometimes when you look at something for a long time, your head just overthinks it, so I thought I'd ask.
Thanks in advance
Garp

Blue · Post by **Blue** » Sat Feb 11, 17 7:56 pm

Yes you should be ok using the earths. It's only when you start using high wattage bulbs that you need to use heavier gauge wiring between the bulbs and the relays.

Garp · Post by **Garp** » Sat Feb 11, 17 8:37 pm

Blue wrote:Yes you should be ok using the earths. It's only when you start using high wattage bulbs that you need to use heavier gauge wiring between the bulbs and the relays.

y

Thanks Blue. The bulbs are the standard 55w I think, so the existing loom and earths should cope fine. Just don't want to have to tear out wiring and replace with new if what's there will work.

Blue · Post by **Blue** » Sat Feb 11, 17 9:02 pm

You don't need to touch any of the original wiring, when you add the relays all you are using it for is the switch the relays on and off, far less load than when it was operating the lights direct. You do need new 20 amp wiring from the relays to your new bulb holders because that's the bit that's carrying the extra wattage. There's no need to cut or alter the original loom whatsoever if it's in good condition.

Garp · Post by **Garp** » Sat Feb 11, 17 9:10 pm

Blue wrote:You don't need to touch any of the original wiring, when you add the relays all you are using it for is the switch the relays on and off, far less load than when it was operating the lights direct. You do need new 20 amp wiring from the relays to your new bulb holders because that's the bit that's carrying the extra wattage. There's no need to cut or alter the original loom whatsoever if it's in good condition.

Sorry to be a tit mate - so the existing loom CAN handle the wattage from the relays to the bulbs.
Is the existing loom 20amp rated ?
I'm literally breaking the loom to "insert" relays, running two 20 amp fuse-able links to the battery for power, running two earths from the relays and adding the new bulb connectors to the ends of the existing loom - therefore, I AM using existing wiring between the relays and the bulbs.
Thanks again

Blue · Post by **Blue** » Sat Feb 11, 17 11:20 pm

PM answered.