A shunt connects in parallel to the ammeter, and bypasses part of the current around it. Here's one that routes 50 amps past the meter, to prevent pegging it out at high current flow.
http://cgi.ebay.com/ebaymotors/Sail...rts_Accessories_Gear?hash=item4cec14e383The main charge leads from the alternator to the battery would attach to the shunt, with medium-size wires attached to the small terminals, going to both sides of the ammeter in the dash. Now, the ammeter no longer reflects the total current flow, which isn't important anyway, but it does indicate whether or not the alternator is charging.
Jerry
Jerry,
That shunt in the ebay listing looks to me like it may have too little resistance to allow a Chevy's Ammeter needle to move. I think that the 50mV mentioned in the listing refers to the Full Scale Defection (FSD)of the moving coil meter it's meant to work with. So with this shunt in a moving coil meter's circuit, 50 amps current flow through the shunt would push a 50mV moving coil meter to it's full reading.
Because the Chevy truck uses a moving iron style ammeter, it has a much higher "raw" FSD (I measured 40 amps on mine with the needle hard over but not pegged), so a shunt with around .33 ohm total resistance still allows the meter to kick over without in pegging with a 63 amp alternator. I think I would go for a .25 ohm shunt if i was using an 80 amp alternator though.
Stuart.
