Partial alternatorfailure at 245 hrs
Thanks to this thread I have determined what is wrong with my transponder, or battery, or VPX Pro...nothing!!! The PP 60 amp alternator that was standard in the RV-10 FWF kit had a partial failure.
For the last 6 months or so the Dynon transponder would trip at random times during nearly every flight. I thought it may have been because of a software update that was done around the same time that would cause the transponder to momentarily draw more current than the 3 amp VPX circuit would allow. I changed it to a 5 amp circuit and the problem persisted. I brought up the VPX page on the AFS EFIS and once saw 37 amps reported on the transponder circuit, ridiculous considering the 20 awg power wires would have become a fusible link at that point but they were fine. With the engine running the voltage was solid at 14.2 and the amps reading looked normal giving me no reason to suspect the alternator.
Then my ETX1200 battery light started constantly flashing. I would charge it on the ground, go flying for a couple hours and by the time I got home the light was flashing again. Obviously a problem with the battery right? Not cool for a very expensive battery that was under 2 years old.
So I pulled the battery and sent it to EarthX last week, installed a PC680 so I wasn't grounded. The next flight the problem with the transponder became constant. I reset it and it would immediately trip. I guess the EarthX battery was providing some masking of the problem.
So Then I found this thread. Today I removed the fairly young Plane power alternator and took it to an alternator shop. They tested it and it showed a problem. They took it apart and found one stator wire broken off that also took out a portion of the rectifier. It is currently still at the shop and they are trying to repair it. The stator is a uni-point part and apparently difficult to find in the aftermarket.
There are no problems with the bearings. For a background on my plane the prop was balanced to .03 IPS before first flight 2 years ago and was checked at the same during the 2 subsequent annual inspections (I have a smart avionics PB3 dynamic balancer). The belt was also torqued properly so neither of those were causes of this failure.
If the lifespan of a PP alternator is somewhere around 200 hours I think I need to look for a different product. Maybe an automotive unit would be better since they would be easy to source just about anywhere. The alternator shop showed me a 14757 that is mentioned elsewhere in the forums but it is larger and heavier than the PP. I'm open to other suggestions.
Colin