Fired it up today for a short flight. Red light on the panel. Discharge on the gauge. I am assuming I have a bad alternator. Is there a voltage regulator in this system? Where is a good place to have my alternator rebuilt? Maybe buy a rebuilt one? I am open to ideas.
Thanks,
Bill

There's an alternator control unit. Not quite the same as voltage regulator. On my MX7-180 it's mounted on the firewall inside the cabin. It supplies current to the field winding on the alternator, which controls the alternator's output. I assume that you've already tried to recycle the alternator side of the master switch without success. There's an inline fuse holder and fuse near the alternator that feeds current to the alternator field winding. It sometimes breaks the wire at the terminal lug due to vibration, which shuts off the alternator. If that isn't the problem, then you might have bad brushes on the alternator slip rings. They can be changed without replacing the alternator.

Had to replace the alternator in our M5-180C last year. The original unit (ALY 8420) was no longer available, so I went with a rebuilt ALY 8520R from Aircraft Spruce:

https://www.aircraftspruce.com/catalog/ ... ysalt1.php

It fit no problem. Photos of the old ALY 8420:

Installed re-built alternator, fired it up, still have red light on panel. Checked inline fuse, which was good. Amp meter shows good charge. Any ideas?
Thanks,
Bill

Wredick, the fuse is usually good, it is the crimps of the wires that get loose and corroded that are a problem.
The older over voltage relays can also short out leaving the red light on even when meter on panel shows ok. The later relays are clear and can be seen on back of panels above the red light at joint of main and sub panels. The older type are a metal box filled with brown material which is poured in liquid then sets up. The inner workings can change position after years and contact the metal box.