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=item4cec14e383

The 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

Last edited by Hotrod Lincoln; 01/31/2010 6:13 PM.
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