Alternator question

HI,

This alternator is on a LUll telehandler, but it is not working. I took a meter and can't seem to get much out of it when it is running , but where would I check?

I assume it would give me 14+ volts between the bottom bolt obviously grounded and one of the top two, but no go.

Any suggestions?

Thanks.

The white wire should have around 13.8 volts. The black cover looks like a regulator, pull the cover and make sure all is clean.