Hi everyone. Bit of time off the site so lets get back on it!!
I've rewired various bits to my s3 in the past example:

Separate glow plug switch.
Spot lights.
Separate switch to power up when turning the key.
What im hoping to find out is all items are direct wired to the battery, im looking to fit a fuse box under in the engine bay for safety realy but what items should be fused/relays fitted and whats the best fuse box to buy. I have the standard fuses under the collum but things have been spured off other wires in the past. Cheers everyone

Just about everything should be fused.
If you can calculate the amps used in each ancillary and make sure the wire gauge matches so it’s safe to carry the load, you can drop ten amps for the fuse in that circuit as the weak link. I have used a blade fuse box in mine that shows an LED on each circuit if it’s blown.



If the amps are going to be more than the fuse box or switches can handle then it’s time to go the relay rout.

Bobsticle said:

Just about everything should be fused.
If you can calculate the amps used in each ancillary and make sure the wire gauge matches so it’s safe to carry the load, you can drop ten amps for the fuse in that circuit as the weak link. I have used a blade fuse box in mine that shows an LED on each circuit if it’s blown.

View attachment 140541

If the amps are going to be more than the fuse box or switches can handle then it’s time to go the relay rout.

Click to expand...

Bobsticle said:

Just about everything should be fused.
If you can calculate the amps used in each ancillary and make sure the wire gauge matches so it’s safe to carry the load, you can drop ten amps for the fuse in that circuit as the weak link. I have used a blade fuse box in mine that shows an LED on each circuit if it’s blown.

View attachment 140541

If the amps are going to be more than the fuse box or switches can handle then it’s time to go the relay rout.

Click to expand...

Cheers Bob

Vehicle wiring products do all the bits

In my experience, the thing that fails most often in diy auto electrics is the wire. It's amazing how many people use under rated wire for heavy loads such as spot lights etc. I'd use a relay for anything over 5 amps.

Col

Think about how you split the circuits into what you need with the ignition on and what when its off, this will determine some of the fuses. Indicators are via ign but hazards are not Also think about what things you could loose together if they are on the same fuse and what you would prefer not to loose. It makes sense to fuse main and dip separately so you don't loose both at once if a bulb blows. I think I split the heater and wiper too as they both draw quite a lot. I put in-line 20A fuses on the power outlets but did not run them through the fuse box as I have a DIY coffee maker that draws 18A and I didn't want it to take out anything else. I have the front and rear fogs on their own cicuit so I they will still work as "get home" lights if i loose the heads or rears. I put in a 2x 5v USB supply that's been very handy for phone chargeing and satnavs:
https://www.ebay.co.uk/itm/Car-Boat...322577&hash=item3607c3a17e:g:-6kAAOSwawpXvRUJ
I tried the cigar lighter types but they burned out, this one has lasted 2 years now, its behind the dash with the sockets by the wiper.