Need help diagnosing charging system (kinda long - sorry)

[Rupester]

I did several searches about charging system and alternator issues, but found nothing that helped, henc I turn to the VAF brain trust.

Over the past 10 hrs flying, on occasion I had a low voltage warning pop up, but in all cases it went away quickly, usually before air could acknowledge the alarm. Most of the time it seemed to occur when the boost fuel pump was turned on, but not always. Yesterday, the alarm began to reappear frequently, on and off, for the better part of an hour. When I went to the EFIS engine page, the voltage was fluctuating up and down from 12.6V to 12.1. ( the alarm limit 12.0). No matter how long I watched, the voltage never stayed steady, it was constantly up and down across 0.5V spread, almost sinusoidal in pattern. I could see the alarm sound whenever the voltage dropped below 12. Turning on the boost pump dropped the bottom voltage in the fluctuation to 11.9V, then it would stay in alarm until acknowledged nearly.
BTW, My voltage is measured at GRT EFIS display #1, and due to the Schottkey diode (AeroElectrics Z-11), has always been less than 13.0 volts.
Today I checked battery voltage (PC680 only 5 mo's old), field voltage at the Plane Power 60A alt, and supply voltage at the B terminal .... all checked out fine. The belt tension torque checks fine per spec. I have tug-tested all wire connections, especially those at the Plane Power plug. No loose connections anywhere that I can find.

So the big question ..... is it time to call Plane Power??

[BillL]

Originally Posted by Rupester

I did several searches about charging system and alternator issues, but found nothing that helped, henc I turn to the VAF brain trust.

Over the past 10 hrs flying, on occasion I had a low voltage warning pop up, but in all cases it went away quickly, usually before air could acknowledge the alarm. Most of the time it seemed to occur when the boost fuel pump was turned on, but not always. Yesterday, the alarm began to reappear frequently, on and off, for the better part of an hour. When I went to the EFIS engine page, the voltage was fluctuating up and down from 12.6V to 12.1. ( the alarm limit 12.0). No matter how long I watched, the voltage never stayed steady, it was constantly up and down across 0.5V spread, almost sinusoidal in pattern. I could see the alarm sound whenever the voltage dropped below 12. Turning on the boost pump dropped the bottom voltage in the fluctuation to 11.9V, then it would stay in alarm until acknowledged nearly.
BTW, My voltage is measured at GRT EFIS display #1, and due to the Schottkey diode (AeroElectrics Z-11), has always been less than 13.0 volts.
Today I checked battery voltage (PC680 only 5 mo's old), field voltage at the Plane Power 60A alt, and supply voltage at the B terminal .... all checked out fine. The belt tension torque checks fine per spec. I have tug-tested all wire connections, especially those at the Plane Power plug. No loose connections anywhere that I can find.

So the big question ..... is it time to call Plane Power??

Sorry to hear of your issues, Terry. Might I suggest two things - one is to remove the plug to the alternator and inspect the connector to ensure it is making a good connection. I have some spares if you need one. Not far by 1st class mail. The PP connector is known to develop high resistance, reducing field voltage and exhibiting the same issues you describe. Sometimes just squeezing the terminal helps for a little while.

Second, if this has no effect, then take it to an auto zone (or the like) and have it tested.

Then - maybe it is time to invoke your PP warranty.

Let me know how this goes - - there are other PP failure modes that may also do this, probably warranty, but also locally repairable. You have my number.