He's saying his ammeter is showing high reading.

Then he specified a volts reading.

That is quite conflicting.

Volts ain't amps.

Mr Natural needs to refine his original post, with more information if possible.

My knee jerk reaction is:

He actually has a volt meter, not an ammeter.
If so:

If you have no secondary issues, then the volt meter is the first suspect. An easy check is to plug in a volt meter to the cigarette lighter socket. You can watch it as you drive and compare.

Telling us the engine is an LS doesn't tell us much about the alternator. Biggest thing to know, internal or external regulator?

Probably internal.

If a second guage agrees with the first, and it is internally regulated, then replace it. If external, then replace the regulator.


Other things to check:

Grounds. Make sure your ground wires are in good shape, and the star washers are great for making good connections.

The plug into the alternator, it is suspect. Was it a new wire harness or a swap? Replacement plugs are available at your local parts store.

Let us know, and good luck.