Alternator Drops out at 900 rpm on Mooney Acclaim.

[Piloto]

No combination of parts will make an alternator churn out more current at low rpm than it is designed to do. 

 

One option is to use a smaller alternator diameter pulley. This will make the alternator turn faster for the same engine RPM. But would impose and added load on the belt. You don't see drop out on cars even at night with headlights and A/C on and on a traffic jam. Cars use a smaller pulley with a wider belt that can take the load.

 

José

[philiplane]

That would be impossible, since it is not belt driven. It is gear drive off the front of the crankshaft.

[M20S Driver]

The problem was found to be a faulty armature in the alternator.  

The alternator was one the first items that was overhauled and it seems like the shop that did it did not find the problem with the armature.

[carusoam]

Thanks for the follow-up.

Best regards,

-a-

[chrisk]

The problem was found to be a faulty armature in the alternator.  

The alternator was one the first items that was overhauled and it seems like the shop that did it did not find the problem with the armature.

I can imagine how frustrated I would be if it was my plane.  Look on the bright side, its working now!  I'd like to know how your mechanic convinced you to re-check the alternator?

[M20S Driver]

I can imagine how frustrated I would be if it was my plane.  Look on the bright side, its working now!  I'd like to know how your mechanic convinced you to re-check the alternator?

Fortunately, this was not my plane.  The shop that maintains my plane was working on this problem after a couple of other shops tried to fix it with no luck.  The update that I got was that Lake Arrow MSC found the problem by starting over from the ground zero since my mechanic had already checked everything. 

[philiplane]

The problem was found to be a faulty armature in the alternator.  

The alternator was one the first items that was overhauled and it seems like the shop that did it did not find the problem with the armature.

There is a very simple check of the alternator coil and the rotor. And these alternators are known to have problematic rotors. It is one of the first things to check when troubleshooting. And there are no published overhaul specs for the lightweight alternator so only Hartzell can repair them at this time.