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apparent alternator issue

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cjay

Joined: 15 Dec 2007
Posts: 53

Posted: Sun Mar 27, 2011 4:57 pm Post subject: apparent alternator issue

I have a vp100 and single alternator, single battery, 2 EFIS chelton system similar to Z11 type wiring diagram.



I'm having trouble with my alternator charging.  Although I have a 50 amp load analysis (if I have everything turned on and max) I have the 60 amp alternator recommended by VAN's, but rarely use more than 30-35 continuous.  Even so, I frequently get battery drain warning  below 12.5 volts, and I have to conserve.  But it is very inconsistent and for some unknown reason it will bounce back up above 13.5 and charge along just fine.    I don't think it is the battery, because I'm not finding any problems on the starting side.  But the problem does seem to be getting worse.



thanks for any suggestions,



ajay

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racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Mon Mar 28, 2011 4:11 am Post subject: Re: apparent alternator issue

A loose / dirty / corroded wire between alternator and regulator can easily fool the regulator into thinking that the battery is fully charged.  Don’t forget the ground straps and make sure that the alternator is solidly grounded.  Easiest first step is to pull and clean all battery connections.  When done, a little petrolatum on the heavy terminals will keep things shiny for a long while.  Look carefully for a loose or broken connection at the small wire terminals on the alternator.   Because of vibration, alternator connections often open up. 



Wires rarely fail in the middle unless rubbing or another form of abuse takes place.  Any wire problem generally appears at the termination.  You could check for excess resistance using a digital voltmeter.  Intermittent problems can be tough to locate, but wiggle any suspect connection and watch for a change in resistance.  



It is possible that a diode within the alternator went bad, which would cut the alternator output by one third, but I doubt it because diode failure is rarely intermittent.  If your wiring checks do not reveal anything, you might consider removing the alternator and taking it down to the good folks at AutoZone.  With their test machine, they can do a quick free diagnosis.  They didn’t even ask me what “car” it was from.  Good luck.

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_________________
Jerry King

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Mar 28, 2011 6:10 am Post subject: apparent alternator issue

At 08:57 PM 3/27/2011, you wrote:

 	  Quote: 	
		  



I have a vp100 and single alternator, single battery, 2 EFIS chelton 

system similar to Z11 type wiring diagram


	


I have the 60 amp alternator recommended by VAN's, but rarely use 

more than 30-35 continuous.  Even so, I frequently get battery drain 

warning  below 12.5 volts, and I have to conserve.  But it is very 

inconsistent and for some unknown reason it will bounce back up above 

13.5 and charge along just fine.



    Your normal bus voltage should be on the order of

    14.2 to 14.6 volts.



     I don't think it is the battery, because I'm not finding any 

problems on the starting side.  But the problem does seem to be getting worse.



    Voltage issues while in flight are never

    a battery issue. If your alternator has

    a built in regulator, then it's a very

    high probability of being bad. The fact

    that your 'normal' bus voltage is so low

    suggests that it may have had some kind

    of problem right out of the box.

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Mar 28, 2011 2:31 pm Post subject: apparent alternator issue

At 08:57 PM 3/27/2011, you wrote:

 	  Quote: 	
		  



I have a vp100 and single alternator, single battery, 2 EFIS chelton 

system similar to Z11 type wiring diagram.



I'm having trouble with my alternator charging.  Although I have a 

50 amp load analysis (if I have everything turned on and max) I have 

the 60 amp alternator recommended by VAN's, but rarely use more than 

30-35 continuous.


	




   When you say "alternator recommended by Van's" is this the

   60A PlanePower product?  When working with alternators

   having built-in regulators, there's not much you can do

   to troubleshoot a voltage variation except to monitor

   the b-lead terminal with a test voltmeter to see if

   readings at the b-lead agree with readings on the panel

   displays. If you have two panel displays and they

   agree to within .5 volts of the b-lead terminal,

   then your alternator is probably in need of attention.

   If the b-lead says where it belongs, 14.2 or a little

   better, then there's a wiring problem. A wiring problem

   that drops 2 volts at 30+ amps is going to dissipate

   some heat. If something 'loose' is your root cause, then

   it's likely to have a somewhat cooked appearance.

   Bob . . .

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cjay

Joined: 15 Dec 2007
Posts: 53

Posted: Tue Mar 29, 2011 6:28 pm Post subject: Re: apparent alternator issue

thanks Jerry and Bob, exactly the kind of advice I was hoping for.  Also thanks for the autozone tip, 



very much obliged,

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