So about 2 weeks ago I was flying along and started having an intermittent low volt light come on with a drop in the voltage to just above 12. It would last a few minutes then go back to normal. I did research and it appears that this could be an issue with the voltage regulator. I have the older model Ducati voltage regular. I checked the connections to it and did not see any corrosion. In my testing since when I first start the engine everything works normally for about 5 minutes. Then I hear a buzzing sound coming from the left side of the instrument panel, the low volt light comes on and the voltage drops to just above 12. The noise will eventually stop and the light go out but the voltage won't go much above 12 and if I fly(I've made a couple trips in the pattern) it drops just below 12. I'm not opposed to changing out the regulator but I'd like to verify it's the problem. All my wiring connections seem to be tight and I would think if it was a corrosion issue it would happen right away not after things have warmed up. I've also seen there is supposed to be a capacitor some where. The only installation I've seen of it it was installed right next to the regulator. As far as I can tell I don't have a capacitor(that I can see). Is there a way to test the regulator? Any idea what's causing the buzzing?

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Yes there should be a capacitor tied to the output of the regulator. Do you have the Rotax engine installation manual? It has a basic wiring diagram. You’ll need it to troubleshoot.  

So what is on the left side of your panel that may be tied to the regulator? Battery master contactor? Relays are the first thing that comes to mind when someone says electrical buzzing. 

After much research and discussions with my mechanic his recommendation was that we just swap out the voltage regulator. I also wanted to add the "missing" capacitor. There have been a few A&Ps that have worked on this plane over the years and I don't know how they missed it. I found some instructions for testing the system and I was able to verify that the stator in the engine is putting out the required voltage. Ordered the parts from Lockwood and downloaded the install manual with the wiring diagram. The capacitor is huge! We installed it and my initial testing looks good. Was only able to do a flight in the pattern because it was windy but I was not getting the low volt light even with everything on while I was taxiing. Going to do a longer flight and verify my voltage at cruise is where it's supposed to be.

So this past weekend I was able to do some more flying. Flew from KHWV to K12N. Volt meter showed good voltage all the way there and back about 2.5 hours. So issue resolved.


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