Avidflyer2
Well-Known Member
- Joined
- Mar 25, 2016
- Messages
- 1,256
- Reaction score
- 441
While taxiing my Piper Arrow PA28R-180, a friend of mine who I was to meet said that he could hear a loud high pitched whine over the engine noise. I could not hear it myself so we swapped places, he ran the engine while I walked around the airplane outside. Sure enough I could hear the whine and when I gave my friend the signal to increase rpms the whine increased in pitch and severity. Knowing that the alternator spins about 3 1/4 times as fast as the engine (Lycoming starter ring gear support 3.25:1 ratio) made me go straight to the alternator first. It wasn't readily apparent that the drive end bearing was beginning to fail as the alternator drive pulley did not have any radial or axial play. I removed the alternator and ordered some new bearings and a brush kit just to be on the safe side. After I got the drive end bearing out of the alternator I could feel a slight roughness in the bearing. I then cut the bearing race into two pieces (air grinder - amazing tool) to see how bad it was inside. The inner race has one small defect and the outer race has an area about an half inch long where the surface is slightly rough. Only one ball in the caged ball bearing assembly has any surface discoloration or surface wear. Thought it might be interesting to you folks to see what it looks like. I've seen overhauled alternators run upwards of $300 to $550, so I feel fortunate to have caught this in time for a simple bearing and brush replacement which cost me about $80 plus a couple of hours labor to remove, repair, and reinstall the alternator. I expect this alternator to go way past engine overhaul now.
