RV8 Whine paired with charging issue.

[Gabe214]

Hey guys, as the title states I had a sudden onset of a whine/RFI noise through my headset and a loss of adequate charging voltage today after taking off in my -8. It has an O-360A1A with a B&C L40 alternator. The whine changes tone with an increase in RPM. It also is very loud when I try to transmit over the radio.

It’s been great since I’ve owned it. I’m a little baffled by this sudden onset though. I checked my headset jacks and grounds, all look right and not touching the airframe. It just started at random in mid flight (about 30 seconds after takeoff).

I did narrow it down to the alternator circuit. When I kill the alternator, the whine goes away and battery voltage drops to about 12 volts. When I turn the alternator back on the voltage goes up to about 12.8 and then steadily drops back down.

Any ideas? I have searched the forum but have not turned up situations that match mine. Thanks for yalls help!

- Gabriel

 

[AlexPeterson]

Sounds like a bad diode in the alternator.

 

[koupster]

Regardless of the whine, your alternators output is well below standard.

 

[Gabe214]

Regardless of the whine, your alternators output is well below standard.

I know it. Earlier it was 13.8V steady and happy. Landed to refuel, fired up and the problem started once I was in the air.

 

[brad walton]

RV8 with a PP 60 amp alternator. I had a whine similar to what you describe. Diodes checked OK. Alternator appeared to be working just fine. No resistance identified in the engine ground. I partially disassembled the alternator and found 2 of the 3 stator wires were broken and arcing. It was still charging at its rated capacity, but arcing across a mm or two gap. I had it repaired by a local alternator shop and it works great again. No noise

 

[SuperCubDriver]

I had the same problem some time ago and spent quite some time to get to the root cause of the whine. Finally I found that at least one diode in the rectifier has burnt through. The alternator failed completely during one flight, only then I found the culprit of the whine. After the repair the intercom was quiet again. This was a PlanePower 60A though.

 

[vic syracuse]

Sounds like the alternator is the culprit. Call B&C. They will take care of you.

Vic

 

[Gabe214]

Sounds like the alternator is the culprit. Call B&C. They will take care of you.

Vic

Sure was. I read your article on kitplanes about the alternator failure. Got it rebuilt at an alternator shop. Cured the problem and was able to not be stranded! Thanks for the help y’all!

 

[ERJDriver]

I've got the same issue, charges at 14.2, but hell of a whine.

It's heard while transmitting and in the side tone