I have a 96 suzuki esteem and the alternator works off and on.
I had the alternator tested at Auto Zone and it is fine but it doesn't charge the battery. The alternator was clogged up with oil from a front seal leak what should I do?
If the alt has oil all in it, the brushes most likely do too, oil insulates electrical contact. If you have an electrical repair shop near have them repair it.
And for head gasket there is no easy fix, you replace the gasket.