revisit to idiots guide to headlamp relays

[tezza]

Good morning guys and gals ; am i right in thinking the relay is powered by all the original wiring i.e. fuse to switch ,switch to flasher/dimmer then on to the relay where the actual power is switched in to power the lights; and please what size wire and what are the s's on the original side of the drawing; please excuse me for being thick!!

[sciroccotune]

The relay is switched by the power (E D I T: one of the 12v+ that connect to a bulb) from the original loom and is powered by the battery.

Think of the relay as an extra switch to connect to a better power source.

remember to fuse the line to the battery.

[tezza]

thanks for that; it clears it up for me

[Red Westie]

Yup....the original dip and full beam feeds (going to the right headlamp) act as the switch feeds to the relays (you need at least two) I'm pretty sure someone mentioned right headlamp feed to keep the full beam indicator function in the clocks.
Then you need good thick power leads direct from the battery (some take their power from the fuse box) to both relays..these need fusing close to the battery. The point here is to use over rated wiring to minimize any voltage drop that may occur between the battery and headlamps so work out the amperage draw and use wire that can handle twice that current.
What you do with it now depends on wether you have two or four lamps? the widely distributed diagram I fairly sure only shows a two headlamp setup.
If you are using a single heavy duty relay for the full beam and have a four headlamp setup the relay will need four seperate outputs going to the full beam ellements in the bulbs, these wires don't need to be as heavy because each is supplying just one 60watt ellement.
Personally I don't rely on any crimped connections, I prefer to solder everything to ensure the best possible electrical joints.
Martin