Ammeter wiring upgrade with a higher output alternator?

[IbanezDan51]

Wiring up my LS at the moment and noticed that the wiring from the alternator first goes to the ammeter then to the starter + post.

Has anyone found the need to upgrade the gauge wire as the stock Datsun wire would have been fine for a 45-50 amp alternator back in the day but with a newer alternator it might be too much?

I might be looking at this totally wrong though...

Cheers,
Dan

 

[morbias]

Don't do it! The ammeter is wired up in parallel to the shunt so doesn't take the full load of the battery / alternator. If your 240z has the shunt on the back of the ammeter (according to the link it might on earlier cars) then you should probably replace it with something more heavy duty and not behind the dash.

Read this: http://www.classiczcars.com/forums/electrical-s30/23030-what-shunt.html

 

[IbanezDan51]

Interesting! Thanks for that.

So it looks like using the stock ammeter with my upgraded alternator will cause the shunt to blow and won't work?

Is there any way of getting the stock ammeter to work or should I look at upgrading to a voltmeter from a later car? In which case does anyone have one of these that they would like to sell me for some beer tokens?

Thanks,
Dan

 

[morbias]

So there isn't a separate shunt unit in the engine bay on 240z's? No idea how it's wired up, looking at the shunt on my 260z it's a fairly heavy duty piece of metal but the actual wires going into it are light gauge in comparison, not sure how that works!

 

[IbanezDan51]

I think the 260Z has a 60 or 65 amp reading on the gauge? I've read that early 240Z's had the shunt on the back.

Not sure to be totally honest. I will try to find a later voltmeter and change to this. Last thing I want now is a dash fire.........

 

[Rob Gaskin]

Read this with interest because I'm currently smash doing some wiring work on my car and have also upgraded to a 280ZX Alternator.

I've also bought a book about wiring Kit-cars and Custom cars.

Anyway the ammeter only shows the current from or to the battery (but not the starting current which bypasses it).

So theoretically if your battery and alternator are in good condition it will read small currents when the engine is running. The battery doesn't need charging and the alternator is supply the load.

A 60A alternator will not be putting 60A into the battery - it will be supplying the load and if it can't it will show a negative reading because the battery is having to provide the deficit.

 

[jonbills]

There is quite a lot of current (even with the shunt) goes through to the ammeter. I'm pretty sure I read stories of fires in the dash...
When I replaced my alternator with a 280zx one I replaced the ammeter with a voltmeter. I think it's safer and more useful anyway.