Plane Power Alternator Failure

I think my alternator regulator bit the dust today. I can hear a whine in the headset that varies with rpm and goes away when i kill the alternator. I checked every conceivable ground including headset jacks. Are these alternators repairable? Seems like it should be an easy fix, but then again its internally regulated, so who knows. Thanks for your help!

You might want to get more information. The whine could be the alternator or something else. A bad diode in the rectifier bridge could result in a whine. The DC voltage is one measurement, then you can measure the AC content of the alternator. - - Maybe this is too much, is there an OReillys, AutoZone etc near that could test the unit? Their equipment will measure regulated voltage, and AC content for the health of the rectifier bridge. That can verify the issue or eliminate the alternator( or one of its many parts) as the root cause.

Also, how many hours on the unit? An alternator is not that complicated internally, rotor, brush holder, regulator/OV, and the diode bridge. If you have a number of hours it might be a good time to replace the bearings (at least on the pulley end) brushes etc. The stator and rotor should last a very long time.

mine failed as well

Plane Power website has a trouble shooting page

http://www.plane-power.com/troubleshooting.php

I started getting a "low voltage" LED indication at 100 hours, but when I checked, the alternator output voltage seemed fine, the aux alternator did not ever come online and my battery remained charged. I went through the trouble shooting schematic on the website and had good bus voltage at the B and field lines. So I contacted Plane Power, and even though I was beyond the warranty, Tommy at Plane Power sent me a new voltage regulator without cost.

Installing this was not difficult, but unfortunately, that did not solve my low voltage indication light issue. I then removed the alternator and took it to a local alternator shop that does auto and marine alternator service. They found two (of four) stator wire broken, after their tests indicated something was amiss. They theorized "vibration" had caused the premature fracturing of the wires, which they repaired.

All is well now: good power and LED is back to off.

It is not hard to remove/reinstall the alternator, and their are bench top options for alternator diagnostics beyond what you can do in situ in the airplane

Thanks for the tips guys. The alternator has approximately 250 hours on it. I think I'll pull it and have it tested on a bench. Would a failing battery display the same symptoms as a failed diode? I read somewhere that the battery absorbs some of the AC current that isn't filtered by the diodes.

rph142 said:

Thanks for the tips guys. The alternator has approximately 250 hours on it. I think I'll pull it and have it tested on a bench. Would a failing battery display the same symptoms as a failed diode? I read somewhere that the battery absorbs some of the AC current that isn't filtered by the diodes.

Click to expand...

No - I don't have data, but would not expect the battery to do much filtering.

Here is a good tutorial on ripple from alternators.

BillL said:

No - I don't have data, but would not expect the battery to do much filtering.

Here is a good tutorial on ripple from alternators.

Click to expand...

That made my head hurt!

We had an issue with using voice out our 496. We will get an alternator whine in the intercom and when we turned of the alternator the whine went away. Turned out not to be the alternator but the voice connection out of the 496. Might look there.
Phelps

yes, when you have ground loop problems it often shows up as alternator whine in audio circuits.

A failing battery can cause the alternator to be always charging and result in the familiar whine being heard thru your intercom and headsets.

The Garmin x96 gps devices are meant to drive a low impedance load, so terminating them with 10 ohm resistors will help reduce noise that is coupled into these lines.

The Garmin supplied cable does not shield the audio lines, so noise from the embedded power wires or RS232 data is easily coupled, but the termination resistors greatly reduce this. Shorten the cable as much as you can as well.