M20F alternator keeps going out - HELP!

[ahineman]

Our alternator on our mooney (1970 M20F with IO-360-A1A) went out about 3 weeks ago after we put about 100hrs on it since buying it. The terminal stud cracked toward the bottom of it and thus would jiggle and loose a connection. So we replaced it with an alternator from Kelly Aerospace (model ALY-8520R).  Within 12 engine hours, the alternator broke in the same fashion.  This time, we noticed that there is was Teflon (that’s my guess) insulator on the bottom of the terminal stud and it had a melted spot on it.  So we tried a 2^nd alternator from Kelly and within 6hrs it failed too in identical fashion.

Our A&P has spent hours talking to Moony ‘experts’ and everything they tell him to test, he has already tested.  He’s also had another mechanic check his work and the failed pieces for ideas.  One would think it’s an electrical system problem because of the melting spots.  However, none of our electronics are failing….no fuses/breakers are blowing….nothing.  Its crazy.  The only symptom is that our ammeter would suddenly show a wavering needle and then slowly get worse to the point where our battery would be loosing  a charge.  We are stumped and not happy.  Any ideas would be great!  Or any leads on someone that might want to buy a used mooney that comes with 3 extra alternator cores. J

 

[KSMooniac]

I think the problem is simple...you chose Kelly alternators.  Kelly has a reputation of putting out CRAP with lots of infant mortality issues.  I would get a refund and try to find a different brand, if that is even possible anymore.  I still have a Prestolite on my J and plan to send it out for overhaul when my time comes instead of doing an exchange and possibly ending up with a Kelly.

[KSMooniac]

Thanks for the tip, Jim!  I'll add them to the list, and I might get the "opportunity" to upgrade sooner rather than later.  I just noticed a crack on the alternator casting where the bolt that holds belt tension goes thru... I'm going to keep flying for now but check it carefully at every oil change, and especially check the belt tension and alternator position every flight.

[randypugh]

I'm not one to bad-mouth any bussiness but my shop says stay away from Kelly with everything. They have had no good products from there. They named fuel pump problems, alternator problems, waste gates and more. I know of an Aerostar with a fresh rebuilt fuel pump (maybe 20 hrs) fail and force him back to a single engine landing. He constantly reminds me of this since I am now only a single engine pilot. Might be somthing to all this talk about Kelly

[Mooneyland]

On an F model I once owned; I had a similar problem. That bird kept eating alternators and no one could find the problem for quite some time. I got tired of $300.00 replacements and started using the exact same car alternator with lifetime warranty. No, I don't recommend this but I had to find the problem and eating $300.00 alternators weekly got old quickly until I had to get creative.

The problem turned out to be the landing light wires chaffing against the metal cowling. Once I replaced the wires and put on a genuine FAA approved alternator, the problem finally came to an end after spending well over 2 grand in alternators.

Fly safe,

Richard Zephro Mooneyland

[Mooneyland]

I forgot to mention that I found where the arching was at night upper cowling off with the engine running. Not easy, certainly dangerous with that prop turning, but what could I do?

Richard Zephro Mooneyland