10 replies to this topic

[ericd2477]

Hi all, I need to repair the Brown wire from Alternator to fuse box

What gauge or amperage of wire will I need  ?

 

[Spider]

Doesn't that wire usually run from the Alternator to he Battery side of the Solenoid ?

 

45 Amp wire is what was originally fitted.

[weef]

As stated above the main power distribution is a cable, normally brown, that comes from the battery side, large terminal, of the starter solenoid.

The alternater has a three terminal plug wih two heavy and one lighter cable. the heavier cables, normally brown and brown with a blue tracer, also go to this terminal, the lighter wire feeds the dash battery charge light.

This power distribution cable size will depend on the model you have but cable sizes/ratings are as follows.

It is better to err on a higher rated cable rating

 

                                                   Cable Size (mm sq)                              Current rating  (amps)

                                                               6                                                           50

 

                                                               7                                                           57

 

                                                               8                                                           63

 

                                                              10                                                          70

[68+86auto]

Looking at 12v voltage drop charts is more important than the wire rating. The amp rating is misunderstood by many.

 

Here's an example...

 

Say you want to run a 10a load using 5m of wire. Standard automotive "10a" wire has 1.13mm² conductor size. The following site calculates the required wire as 2mm² with a 5% voltage drop. If you were to use the "10a" wire, you'd have an unusable voltage at the load. This also doesn't take into account the heat of the engine bay. https://www.fabhabs....zing-calculator

Luckily for a mini alternator the wiring is only about 1m so the amp rating should be an ok indication. It's an important detail when a longer wire is required.

Edited by 68+86auto, 27 February 2025 - 05:27 AM.

[Steam]

Current rating is not so much misunderstood as misread. Current ratings come also with a length component that is 10A per 5 metres or wharever. Also misread is voltage type, frequencies and voltage level.
Current rating is fine if you follow all the relevant modifiers.

Edited by Steam, 27 February 2025 - 06:07 AM.

[ericd2477]

Just to clarify which wires I am going to replace - Looking at 1988 onward carburetor loom. The brown wires that come from alternator to Starter solenoid and the brown wire that comes from starter solenoid to fuse box , and the brown wire from starter solenoid to ignition

Edited by ericd2477, 27 February 2025 - 10:07 PM.

[68+86auto]

Just to clarify which wires I am going to replace - Looking at 1988 onward carburetor loom. The brown wires that come from alternator to Starter solenoid and the brown wire that comes from starter solenoid to fuse box , and the brown wire from starter solenoid to ignition

 

There's a splice in the wire between the solenoid and interior.

[Spider]

Here's some links to some good info Dave posted up some time back that might be of help;--

 

https://www.theminif...cable-listings/

https://www.theminif...trical-circuit/

https://www.theminif...ng-codecolours/

 

[viz139]

Wire gauge is used more in the USA ,in Europe wire size is usually in mm2.(square millimetre).

Your cable would be

6 mm2.

10 Gauge

84/0.3 stranded flex

42 Amp cable.

[68+86auto]

There's an important detail missing. What size is the alternator?

[PoolGuy]

Current rating is not so much misunderstood as misread. Current ratings come also with a length component that is 10A per 5 metres or wharever. Also misread is voltage type, frequencies and voltage level.
Current rating is fine if you follow all the relevant modifiers.

That's cleared it up then...