Two days ago when returning from a test flight with my new prop I got a flashing red light on my RMI engine monitor. It said I had low battery voltage. Taxi-ing in after landing I was showing battery discharge. Yesterday I pulled the cowl and started troubleshooting. My first inclination was that maybe the brushes were worn down since its over 30 years old, and so I stuck a DVM on the field output of my regulator. Instead of showing the typical 4 ohms it was varying anywhere from 20 ohms to 60 ohms, especially when I touched the V-belt. I removed the alternator, pulled it apart, and sure enough, the forward brush was barely making contact. I found a starter-generator-alternator shop close to the Santa Maria airport who had not only the brushes but the front and rear sealed-bearings, which were dried out. He removed the bearings from the shaft and front cover, installed the new ones, and only charged $19 and change with taxes. Finding that shop sure made things a lot easier!