780 Champ supplemtal steering issues

We have two 780 series III champions and both are experiencing supplemental steering issues. I'll just start with one for now, haha. So when you turn the key on and the "charge pump" comes on to allow you to push the clutch pedal in and disengage the hydrolics, then doesn't it go off unless it senses low voltage? Anyways its not going off and the alternator isnt charging, i bought a new one thinking that was the issue but it made no difference, so the machine is very hard to steer like its only running on the supp steering pump and not charging.....any ideas or ayou know anyone to try and call that would be savy on the subject?