REFLECTOR:Alternator Failure

[Scott Derrick]

Well,

This one was a doozy!!  The alternator shop that installed the pulley on 
the new alternator(4 months ago) fubar'd the installation. The new 
alternator had a bit longer shaft and the nut bottomed out at the end of 
the threads before completely compressing the lock washer.  This allowed 
the pulley to slide back and forth just a bit under load.  After a while 
it wore the pulley and the shaft enough  to start wobbling around and 
spinning on the shaft.  The alternator and pulley was thrashed, as was 
one of the mounting ears from it vibrating. Only a 90 day warrantee 
because it was installed on an airplane.  I found a rebuilt one with a 
new pulley for $60(different shop).

The good thing is it let me know before hand. When on downwind yesterday 
I hit the Gear Down switch and the  Low Voltage alarm came on.  Hmmm... 
I said.  I looked over and the voltage was 12.6, the alternator showed a 
33 amp draw.  I  clicked of the landing light and the alarm went off. 
The gear finished coming down and I put the light back on, all OK. 
Hmmm.. I thought.  About 30 minutes prior I had made a low approach to 
verify compass integrity(Yeah right!@), it had nothing to do with the 
group of kids visiting the airport that were lined up next to the 
runway!  I had turned on my landing light during the low pass and 
neglected to turn it off for the remainder of the flight.  Still, the 
alternator can well handle the draw of the light and the gear motor.

This morning I fired up and the low voltage alarm came on right away. 
If I idled at 700 rpm it would go off, but as soon as I revved up the 
engine, the amps would drop to zero.

That ol pulley was just free spinning on the alternator drive shaft!

Scott