how do i know what amp wire to use on the electrical items on my car?

for instance,

The Fan, all it says on it is 12v DC, how do i know what amp wire to use, i would hazard a guess at 5,8 or 13 ?????

The Alternator,

I am using the Denso style alternator, again it requires a 12v supply, how do i know what amp wire to use, 5, 8 or 13 amp or different?

thanks again

Alex

[Edited on 18/9/10 by omega0684]

Somebody who has built looms more recently will be along soon but my thoughts are that both of them items are high current and more than 13A.

Fans draw large currents to start then drop off. Alternator pull alot but does depend on if you are running heaters, wipers or anything else.

HTH

quote:

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Originally posted by bi22le
Somebody who has built looms more recently will be along soon but my thoughts are that both of them items are high current and more than 13A.

Fans draw large currents to start then drop off. Alternator pull alot but does depend on if you are running heaters, wipers or anything else.

HTH

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I guess your talking about the Exciter wire for the alternator? if so then you'd get away with 1mm thin wall automotive cable for that (16amp)

For the fan again you'd get away with 1mm thinwall, but if you ever upgrade your fan to one of the high power facet fans, you'd be better of with 2mm automotive thinwall (25amps)

So if you want to be uber safe then get some 2mm from vwp or the like.

Chris

sometimes a google search of part numbers can identify a datasheet giving you current information. failing that i used a multimeter to measure the current.
wire the meter in series with the fan and used a battery or jump starter for power, a mx5 fan drew 5.5 Amps. I did not notice a high start up current but this may be the meter (Digital) being slow to show the reading. Remember to only do this for a few seconds as some multimeters don't like extended periods in current mode.

This might give you an idea
http://www.merlinmotorsport.co.uk/images/coolingl/14InchSlimlineFan.pdf