What Amp Wire Do I Need?

[Guest Ian Maycock]

I need to replace the wires from the back of the ignition barrel as the current ones are too short. What amp wire do I need?

[Dave R]

depends if the switch is doing all the work, or all the circuits off of it are via relays

[Guest Ian Maycock]

It is the wires that are soldered to the terminals off the ingition barrel. I have since measured the diameter and done a little more research and have found out that the larger diameter wires are 35 amp while the smaller diameter wire is 8 amp.

[blue]

Watts ÷ volts gives amps

[agent_zed]

when i hear questions about amps and watts i think of this

 

 

which is hilarious

 

although doesn't answer your question in anyway sorry. If it was me i'd prob do what you have done and measure the diameter of the wire and replace like for like and you probably won't go far wrong.

[sj-bradley]

And then there's the classic ...

 

https://www.youtube.com/watch?v=kTcRRaXV-fg

 

 

Simon.

[Guest mchi3am2]

Without any diagrams or ideas of what you have attached to the ignition barrel, my answer will be somewhat vague.

 

Generally speaking, the larger the cable, the bigger the current capacity (voltage capacity is a bit irrelevant as far as cars are concerned - ignoring HT and sparking circuits).

 

From the details you've provided I would guess that your 35 Amp stuff would be 4mm2 Cross sectional area and the 8 amp stuff would be 0.5mm2 cross sectional area.

 

As a general rule of thumb, you should always go with the bigger cable size since a cable might be able to take 35 amps when in free space, by itself. But might not cope if its jammed next to lots of other 35 amp cables, hidden in a nice warm void. Generally you can't have a cable that is too big, but you definitely can have a cable that is too small (think fire here).

 

Either way, I think you would be looking for 4mm2 CSA cable, based on what you have written.

 

Bear in mind that you want to get multi-stranded cable, not single core (like the standard twin and earth that houses use) since this is likely to experience vibration during its lifetime and single core is NOT going to cope with significant vibration.

 

The other thing to check to get an idea of expected load is what the fuse is rated at. If it's rated at more than 35 amps, you'll need a bigger cable (6mm2 is the next size up and will take about 45 amps, again depending on installation).

 

Once you've done it, check the load with a clamp ammeter and at least that way you'll know.

 

I'm not sure if the above helps, but hopefully it gives you some idea of what to look for.

 

Andrew

[sj-bradley]

A word of warning about clamp ammeters. Most of them are for AC only and would NOT display the correct reading (if any)

 

You need a DC clamp ammeter as the majority of circuits in the car will be DC only.

 

(AC - alternating current like in a house etc there is no "+ve" as such, DC - Direct current between +ve and -ve like a battery etc)

 

Simon.