guys,

i dont have a clue when it comes to volts/amps etc but do understand that running it wrongly can result in melted wires/fires so my question is this, what size cables should you be running for things like additional 12v cig sockets, fog lights, DRL lights? i know they will all draw different currents so wasnt sure what type of cable to buy and keep for any 'project's i may decide to take on - should i get a 'one size fits all' cable or different rate cables?

a handy guide would be great!

Sal if I get the chance I might throw a few numbers together for you.

There are a few factors that should be considered when running a cable. Voltage drop is one of them, this can be calculated for any given cable size and current and the only way to reduce voltage drop is by putting in a bigger cable. Probably not a problem to most DIY car electrics though.

The biggest factor really is current carrying capability, you really need to know what power you are looking to draw and work out what you need - there is no point in running a massive cable for the likes of DRLs as you will probably find terminating it more difficult and it's just unnecessary.

You will notice that most car wiring is done in gauge not cross sectional area. Also car wiring tends to have thin insulation but it's of a better grade than standard pvc so can withstand more heat.

Thanks mate. No rush. I thought a little guide would help others too who may try out some diy who may not take the different factors into account!

must admit, my standard rule is this...

If its for an LED - use speaker wire, if its anything else, use 18 gauge wire.

So far my car hasnt gotten warmer than planned!

Sal, I forgot all about getting back to you but I will list a few common sizes here.

0.5mm² - 22AWG - 11 Amps

0.75mm² - 20AWG - 14 Amps

1.0mm² - 18AWG - 16 Amps

1.5mm² - 16AWG - 21 Amps

2.5mm² - 14AWG - 30 Amps

4.0mm² - 12AWG - 41 Amps

6.0mm² - 10AWG - 53 Amps

10mm - 8AWG - 70 Amps

Automotive wiring is tri-rated, usually up to around 105°C (IIRC). Cable can either have a standard wall thickness or in most cases its thinwall. Care should be taken when choosing a conductor size, length and voltage drop should be considered. Current capacity of the cable should be higher than the rating of the circuit protection.