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Andy475
 Post subject: Alternator Field Issues
PostPosted: Sun Jun 14, 2020 2:46 pm 
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Hey Folks,

I had the alternator field fuse blow in flight the other day, far from home, so we set down and fished the old fuse out. We replaced the fuse, and it was charging on the ground fine, so we flew it and about 4-5 minutes in it blew again, and turned back. My initial thought was a chafed wire grounding it out. Due to being away from our tools and shade, there wasn't a lot we could do to diagnose it. We visually inspected the field wire and rebundled it in case we missed something. It checked out on the ground during the run up again but then promptly blew 2-3 minutes into a test hop. The trend here seems to be high power sustained power settings which leads me to believe its an internal alternator issue. While I work on getting all the tools (and sunscreen) together to chase this, any immediate thoughts come to mind or trouble shooting pointers? These hard to replicate gremlins are always great fun....

-Andy


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thorpdrvr
PostPosted: Sun Jun 14, 2020 4:01 pm 
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Does it have any sort of over voltage protection either in the voltage regulator or wired in separately? If so, it is doing it’s job by popping circuit breaker or blowing fuse to protect from over voltage situation. I would check ground on regulator and condition of wiring if it’s not the built in type. My guess is ground issue or bad regulator.


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Andy475
PostPosted: Sun Jun 14, 2020 8:09 pm 
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It has an internal regulator (he says confidently after having searched the entire airplane twice over for it). The troubleshooting process didn't take long, the once I got ahold of a multimeter it became clear the alternator had shorted. I suppose that's better than a chafed wire deep in some cranny of the aircraft.

Szekely,
Andy


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speedbird1
PostPosted: Mon Jun 15, 2020 7:32 pm 
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Andy,

You don't say what alternator you have, but I have a Prestolite ALY-8420R for sale if you need that type? It was removed to install a lightweight model.
Speedbird 1

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Fraser MacPhee
PostPosted: Tue Jun 16, 2020 10:15 am 
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I am an electrical novice to say the least - I excel at plugging things in to outlets and little beyond. I think I pee'd on an electric fence once on a dare - ever since, our relationship has been strained....I do however, have experience knowledge that a crappy battery will pop the field wire circuit breaker.

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Fraser MacPhee
N926WM
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Rich Brazell
PostPosted: Tue Jun 16, 2020 10:30 am 
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Frase...are you sure you didn't pee on the battery ?

RB O0


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Fraser MacPhee
PostPosted: Tue Jun 16, 2020 10:37 am 
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Positive Rich - you ride the lightning with your weenis one time only.

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N926WM
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Andy475
PostPosted: Tue Jun 16, 2020 10:36 pm 
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Joined: Sat Aug 05, 2017 11:52 pm
Posts: 35
Hey Speedbird, I'm running a small diameter plane power alternator with a mounting kit for my dinosaur 0-320 (its a really early case). I ordered up a one-for-one swap, as the extra cost in making a different model fit would likely exceed the savings. The time/money equation is also playing into this, as I have no time (and limited tools on hand)!

Szekely,
Andy


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Andy475
PostPosted: Tue Jun 16, 2020 10:36 pm 
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Joined: Sat Aug 05, 2017 11:52 pm
Posts: 35
Hey Speedbird, I'm running a small diameter plane power alternator with a mounting kit for my dinosaur 0-320 (its a really early case). I ordered up a one-for-one swap, as the extra cost in making a different model fit would likely exceed the savings. The time/money equation is also playing into this, as I have no time (and limited tools on hand)!

Szekely,
Andy


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speedbird1
PostPosted: Wed Jun 17, 2020 2:48 pm 
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Hi Andy,

In which case I am no use to you are my Prestolite was removed to fit a lightweight one onto my IO-360-A1A.

I anyone needs one you know where to come!!

Speedbird 1.

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200hp Lycoming


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