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-   -   Alternator non-failure and Dynon (https://vansairforce.net/community/showthread.php?t=81202)

Greg Arehart 01-12-2012 09:41 PM

OK, the answer (or so it appears). My digital voltmeter seems to be not working, thus the funky reading on the battery voltage. A second (analog) meter gave me about 12.5 volts on the battery today (as opposed to 13.5-13.8 on the digital one), which is closer to being in line with the Dynon reading.

Second, and original, part of the problem was the dropping voltage and discharging of the battery in flight. Turns out that the alternator field fuse was blown, and after replacing it I am getting the alternator charging the battery again. So obviously it was not a direct short circuit. The mystery to me is why this blew after 450 hours of service. Apparently Continental engines have this occur not uncommonly, and replacing the fuse/resetting the breaker is SOP for those engines.

Chalk up another "experimental airplane learning experience" for me.

Cheers,
greg

frankh 01-12-2012 10:16 PM

Cool!
 
Well that was easy...:)

Frank

Alan Carroll 01-13-2012 07:35 AM

Glad to hear it was cheap fix. The fuse blowing seems kind of odd though; have you rechecked the field wire and its connections? What kind of alternator?

Greg Arehart 01-13-2012 07:56 AM

Alan,

Yes, I checked the field wire and connections including a resistance check. Everything looks good as far as I can see. I will be flying it this weekend and looking to see if it happens again. Plane Power alternator.

Greg

Alan Carroll 01-13-2012 08:03 AM

You might want to keep an eye on the voltage. According to Plane Power's instruction sheet it has built-in crowbar protection. This works by tripping the 5a circuit breaker (or fuse in your case) if over-voltage is detected. Could be you had a momentary over-voltage event?

rvmills 01-13-2012 10:59 AM

Input (and offer of assitance at the aeropuerto) deleted by poster...didn't read page two of the posts, with the fix (duh!) Glad you got er dun Greg!

Cheers,
Bob

Greg Arehart 01-13-2012 12:57 PM

Agreed Alan. I will be keeping a close eye on things for the next couple flights. Not sure what would have caused a voltage spike, though (hoping the alternator is not failing in some manner....)

Greg

RV6airplanePilot 01-13-2012 07:06 PM

Brushes wear fast
 
at altitude and in our engines with higher vibration. I installed a new 70 amp Nippondenso alternator a few years ago. After about 500 hours the brushes are worn to the replacement point and it started to vary the voltage more. Now I plan to replace the brushes every other year. It is easy.

Ron Lee 01-13-2012 08:17 PM

Here is one link that discusses replacing the brushes

http://www.sparkys-answers.com/2010/...lternator.html

Any idea on the best quality brushes?

Walt 01-13-2012 08:32 PM

The PP field can easily draw 4 amps, you may consider a 7.5 amp fuse to eliminate nuisance fuse blowing (or circuit breaker popping).


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