Regulators are intermittent

[MrNomad]

The Nippon alternator in my RV9A spiked to 14.5v, then 16, then back to 14 while in flight. The Dynon started to alarm so I turned off the ALT FLD and flew it home on ship's power. Once on the ground, I tested it but voltage remained at zero.

I took the ALT to a local rebuilder who bench tested it and claimed it was working OK (what??). I asked him to change the internal regulator anyway & test it again. Of course, after the new reg it still worked on the bench.

I put it in the airplane and flew it for the first time today. It locked into 14.0 to 14.1v and never varied. Whereas the old reg went higher occasionally, the new unit locked in right around 14.1 volts.

I must conclude that regulators, even though they are transistorized, can develop intermittent problems.

Barry

PS: My thanks to Charles from FL for his advice. This is a great community!

[chaskuss]

Barry,
Bench testing is not always reliable. Most intermittent failures of solid state devices are thermally or vibration activated. Short of applying a heat gun to the alternator while on the test stand, you often can not duplicate the environmental factors which contribute or cause the failure.
Glad to hear you got the issue resolved.
Charlie