relay for lights installation

[Henryfiat]

Bought the relay,new headlamps and bulbs and ready to install. Can anyone give me some advice on installation before I screw something up. Hope all is pretty simpl .

[temason]

No replies?! I'm about to do the same thing - please pass on any tips - I think pretty straightforward but I haven't looked too closely yet
Thanks!

[courtenay]

Here you go... http://www.fiatspider.com/f15/viewtopic.php?f=6&t=31982

[707kevin]

It's simple, and it's not Fiat or 124 Spider specific.

The goal is to increase available voltage to the headlights by reducing the number of items causing voltage drops.
Long, undersized wire is one. Headlight switches are another. All the connectors in between add up as well.
Factory headlights go from battery, to multiple connectors, fuseboxes, more connectors, headlight switch, more connectors, finally to the headlights.

With relays, you just go from battery, to relay, to fuse, to headlight. And you add larger wiring for less voltage drop.
The relays really just turn the headlights on and off for you with a much shorter and more efficient path for the voltage.
Then you use the existing headlight circuit to turn the relays on and off. The draw of the relay on the switch side is so low that the inefficiencies of the factory wiring don't matter anymore.

If you already have crimps and connectors and relays and fuses and wire laying around (some of us do.) then it's an easy DIY job. If you don't, it's well worth it to but the relay harnesses that essentially just plug in between your headlights and the existing plugs.

[707kevin]

http://electronics.howstuffworks.com/relay.htm