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MG MGB Technical - Relays and headlamp wire gauge

Hello all. Still restoring a '72 bgt. Will be installing headlamp relays and associated wiring. Couple of questions: 1 - can I use the stock headlamp wire or do I need to go a size larger and 2 - can I run the wires to the headlamp pigtails or do I need to eliminate the pigtails and run the wires directly in to the headlamps.

Thanks, Tom
Tom Custer

I have used the pigtail and existing wiring with no problems and nice bright lights. You will need to install a new wire to bring the power for the headlights to the relays. I connected mine to the brown wires at the fuse box, you can also connect to the battery cable at the starter solenoid if you wish.
John H

The original wiring should be fine, but when I added relays I wired them to the connectors by the right-hand headlamp rather than cutting into the wiring. This means the long run from the switches to those connectors is only operating the relays, and the high current of the headlamps is only in the tail of the right-hand lamp, and the cross-wires between the headlights and tail of the left-hand lamp.

Definitely replace the bullet connectors by the headlamps, polish the bullets on the harness and tails, and assemble with Vaseline.

I would *strongly* recommend you fit individual filament fuses between the relays and bullet connectors by the right-hand headlight. If you don't fit any fuses, and there is a short at a headlight, you will do more damage to the wiring than the original setup, as the new setup allows significantly more current to flow in practice. If you only fit one main supply fuse, and it blows or fails, you will lose all the headlights unless you have the presence of mind to pull on the headlamp flasher.
Paul Hunt

John and Paul, thanks for your comments. Good tip on the fuses Paul -- I was wondering about that.

Thanks again, Tom
Tom Custer

This thread was discussed between 15/09/2008 and 16/09/2008

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