Hi all.

I am upgrading my alternator in the 180b to an 85 amp unit and have read on here and elsewhere about the importance of upgrading the 3 main wires when doing this.

1) neg battery terminal to chasis
2) chasis to engine block
3) pos battery terminal to alternator.

I am confused because instead of pos bat to alternator. I have pos bat to starter motor. The positive from alternator seems to work its way up to the main box of relays. Also my engine block earth goes straight to the neg bat terminal instead of the chasis.

Any help appreciated

Cheers
Cam

the way you have it is right +bat always goes to the starter as it has the most current drawer. the charge wire goes to the fuse box because it is fused
(i think, and if not it should be).
it dose not mater what order the grounds are set in as long as both the engine and chassis are BOTH grounded

Sweet thanks.

ok so I will replace both the grounds but which of the positive wires should i upgrade. Bat to starter OR alt to fuse to bat, or both.

Also is this all really necesarry as the standed wiring really didn't seem all that much thinner than the stuff on the vn the alt came on.

if its all in good nick i wouldn't bother but make sure that it is fused because the last thing you wont is to fry your wiring harness

cheers
mate,

should I put the fuse on the wire from the alternator to the bat, and how big should the fuse be do you reckon?

I'm a little confused. If the alternator makes 85 amp i guess i'd go for a fuse around this size, but if the wire can't handle 85 amp a fuse won't really help.

Is it in case the alternator spikes (can they do this)?

The golden rule is the fit a protection device to safe guard the rating of the wiring.
So, if the stock alternator output was, for example, a 40A unit then the existing wiring should be capable of handling that 40A, so it should be protected with a 40A device.
This is the inherent danger of wacking in a high output alternator and connecting it to existing wiring not capable of handling what the alternator is capable of producing
Can you spell "FIRE"
I recommend to insert an inline maxi fuse [easily maintained] or fusible link [not so easily maintained] to protect the wiring and fit that device at the Alternator "A" terminal, in series with the wire[s] that go to the fuse block[s].
My recommendation for additional wiring which dictated the upgrade in the first place, is this: - This auxiliary power feed system can be quite simply overlaid on the existing wiring but will protect that wiring from the new current loads.
You can use the latest technology wires, relays and protection devices knowing that the wiring is dimensioned correctly and protected adequately.

It is the LOAD that consumes the current from the Alternator, the battery only wants a trickle current to keep it charged up so it can crank the engine next time you want it to.
In normal circumstance that is usually the current resulting from a 14V alternator voltage feeding into a 12V battery so its only a 2V P.D. and a few amps, depending on the battery condition.

The gauge cable from the battery to the starter needs to be adequate but only for the characteristics of the starter motor used.
The engine earth [Ground] cable must be the same gauge since it will handle the same current back to the battery as the supply cable does to the starter.
Upgrades to these two cables would only be necessary if the original cables were under dimensioned and you experience slow or erratic cranking.

I like an Ammeter in the circuit so I can see what is going on

Clear as mud

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Sorry Nissanman. This seems like great advice but my knowledge of electronics is very poor. I have read it 4 times and am really struggling.

If I was to do the following would my car be safe (money and time aside this is my primary objective)

1) get some cable capable of handling say 120 amp.
2) use this to replace the cable from the bat to chasis, block to chasis and pos bat to starter
3) run a new cable (same 120 amp) from battery to alternator A terminal (not using the existing fuses/relays)
4) fit a 100 amp maxi fuse in series with the new alternator cable going to the A terminal.

Cheers
Cam

Your proposed upgrade for the cables sounds fine.
Can't do any harm.
Just remember that there is NO FUSE fitted or needed in the battery + to the starter motor.
It only handles the high starter current draw briefly and is dimensioned appropriately.
The protection is required where the alternator output feeds the remainder of the car.
If that is attached to the "A" terminal normally, then that is where the protection should be fitted.
If you need a few more diagrams let me know

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Thanks Heaps