Jim -

There is a good chance that the problem is at the alternator end, not the dash end. On the 240 alternator, which I think is the same for you, the exciter wire is red, connected to a spade lug on the back.

The alternator needs that wire, a fat wire that carries the charging current, and a ground wire between the alternator frame and the block. The amp light needs the thin red wire and the ground wire to light.

On the inside of the LF fender is a large connector, big enough to hold 8 wires. It looks like the one the 240 mounts on the firewall, and the thin red wire goes through that to get into the cabin and thence the dash amp light.

If you decide to test the amp light, remember that the excitation voltage is less than 12, so care is needed to avoid overloading.

Good Luck,

Bob

:>)