Hi all,

Jumping in at the deep end here and decided to build a new loom for the locost. I have read through and seen that most people seem to be using very few relays, in fact only really for the main lights which surprises me, but if you have a 15/20/25a rated switch then I can see there may be no need. Does this tend to be the general concencus?
Now I've spent a few hours looking over where to start and can't quite work out best practice - is it to put the relay post fuse and take a spur from that to the switch side of the relay so the whole relay is on the one fuse, or to just fuse the high current feed and not fuse the switched side?

I know this might seem like a pretty basic question but I don't want to get this wrong!!

Cheers

Ben

I have 4 relays, 1 being the Flasher , 2 being the lights, 3 being the fan 4 being on from the ignition to the lights to stop me leaving the lights on as I got fed up with catching the stalk on getting out of the car and didnt want to come back to a flat battery

Everything should be fused IMHO.

I put relays in the horn feed and fan feed as they draw a fair bit of current and also lights and switched ignition feed. Basically, everything that goes through the stalk switching.

Ive got one relay, on the indicators. thats it

I have 5 relays and everything is fused. For electrical safety and to prevent fires everything needs a fuse.

It is a trade-off, in my opinion: you get a lot less wires and less potential problems with loose wires with less relays, but you lose some safety. I have several now, after going through lots of broken wires and burnt things (not good...).

Hi Beam (main beam for you)
Lo Beam (dipped)
indicators
horn
rad fan
wipers
starter

It puts a lot less current through your switches if you wire them correctly, and I would hope, have less chance of a fire. Do think about how you are going to mount them all; mine are all over the place under the dash, and should ideally be mounted on a piece of ally, all in one place. I might change it all next year.

I always use good quality, high amp, switches rather than relays, It's much simpler.

thanks for all your replies people, good to get a guage of whate veryone is doing. I've got the advantage that there's no need to worry about any road legal stuff as it's destined to be a track monster. Think I'm gonna go with fusing the feed to both the switch and therelay.


time to purchase some leccy products!

Also consider that using just switches, even of the correct rating (or better), you will have a longer wiring run, and need to use thicker wire over the full distance.
Using relays, you can use thinner wire for the switching, and have shorter runs of the thicker more expensive wire.
Also consider the volt drop over the entire cable length with not using relays (could give you a dimmer headlight down to the volt drop).

IMHO use relays where possible for heavy current items.

It also reduces the current arcing and wearing / burning the switch contacts (even on correctly rated switches) thus increasing the switch life.


IMHO every circuit should be fused at the source.
The nearer the battery the fuse, the less likely for wiring faults (shorts to earth etc) will burn out your wiring, thus reducing the fire risk to your car.