Barrus (Mitsubushi) 80 watt alternator, Stirling advanced regulator - both about 8 years old, 1700 hours.
I noticed while cruising along the domestic voltage on the Smart guage was reading 15.2v, also the high voltage light was on on the controller. Stopped the engine, re-started, no problems, normal voltage but kept rpm low. Back in the marina found a small wire from the back of the alternator, which connected to the main battery feed stud, had not been crimped correctly and was loose. I remade the connection and cleaned up all alternator connections. Ran the engine for about 10 mins at various revs, all normal.
I have a battery charger on shoreline and this keeps the SOC 100%. This weekend took the boat out and after a few minutes at low rpm the low voltage buzzer came on and stayed on, and domestic voltage was down to 13.5 from approx 14.4. Stopped the engine, re-started, buzzer and voltage still misbehaving. At 1200rpm, buzzer beeped every 2 seconds or so. Rechecked all connections and found satisfactory. Found by putting the headlight on the buzzing stopped, even at tickover and voltage was normal. SOC 100%.
Next day, after using the inverter overnight, SOC 76%, buzzer and voltage normal, even when SOC up to 100% and no headlight on.
Do I need the alternator or Stirling regulator tested? Any other suggestions? Thanks!