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How to check an alternator??

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mattreeves(at)yahoo.com
Guest

Posted: Sat Sep 08, 2007 4:13 am Post subject: How to check an alternator??

Okay, I wired my ammeter backwards and here's what happens.

   

  I start the plane and the ammeter is on the positive side slightly.

   

  I turn on NAV lights, strobe lights, landing lights and the ammeter goes MORE positive and stays there and the voltage goes from 15 to right around 14.   Turn off everything, the voltage goes to just under 15 and ammeter goes to zero.

   

  So I don't think my ammeter was wired backwards.

   

  It appears my alternator is charging normally but I think my ammeter needs to see a therapist.

   

  Matt

   

  



"Robert L. Nuckolls, III" <nuckollsr(at)cox.net> wrote:

  [quote]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"  



At 04:30 AM 9/2/2007 -0700, you wrote:



[quote]Hi Bob !!

Thanks for the help and suggestions !! I really appreciate you and all I 

learn from you.



So, I did exactly as you said, and you are 100% correct. I left on a 

bunch of stuff for about 10 minutes, then started the plane and 

immediately noticed the ammeter was slightly on the negative side, maybe 

reading about 4 negative amps. The voltage read just under 15 volts - 

say 14.7 the whole time and stays there but within about 3 minutes, the 

ammeter came back up to zero and stayed there.



I wired the ammeter and external shunt as per Van's Aircraft instructions 

and my brother Danny (which you've all heard from many times) says there 

are 2 other ways (according to Dynon) to wire the ammeter which I might do.



I'm not sure of the best or correct way to wire the ammeter [quote][b]

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nuckollsr(at)cox.net
Guest

Posted: Sat Sep 08, 2007 6:32 am Post subject: How to check an alternator??

At 05:12 AM 9/8/2007 -0700, you wrote:



 	  Quote: 	
		  Okay, I wired my ammeter backwards and here's what happens.



I start the plane and the ammeter is on the positive side slightly.



I turn on NAV lights, strobe lights, landing lights and the ammeter goes 

MORE positive and stays there and the voltage goes from 15 to right around 

14.   Turn off everything, the voltage goes to just under 15 and ammeter 

goes to zero.



So I don't think my ammeter was wired backwards.



It appears my alternator is charging normally but I think my ammeter needs 

to see a therapist.



Matt


	


    We need to see the schematic as to how your ammeter is wired.

    The classic battery ammeter is wired between the bus and the

    battery and all loads run from the bus side, all power is fed

    to the battery (via alternator) from the bus side. Hence, the

    minus-zero-plus ammeter is a indicator of rate of discharge/charge

    for the battery. Alternator off and all things on, the ammeter

    should show not slightly, but significant discharge left of

    zero. Alternator on after starting and then recharging a

    taxed battery, the ammeter should show a significant charge

    of the battery that subsides with time.



    You've consistently used "slightly" to describe ammeter

    movement and you've yet to give us words that suggest that

    the ammeter is in a position to properly sense and display

    the charge/discharge conditions cited above.



    This gives rise to two, possibly concurrent conditions:

    (1) the ammeter is the wrong size . . . expects to see

    much larger currents than your system experiences such

    that all indications are "slight" versus "significant".

    (2) the ammeter may not be properly positioned in the

    system. You need to acquire specifications for the

    ammeter and deduce whether or not it is wired per the

    instructions that came with it.



    Is the ammeter "calibrated"? I.e., does it have the

    word AMPS on the front? What is the full scale value

    on the face? -30 to +30? -60 to +60? Does this device

    have a shunt or just two fat wires that carry all the

    current to be monitored?



    Bob . . .

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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Sat Sep 08, 2007 1:34 pm Post subject: How to check an alternator??

Matt MORE positive under more load = ammeter is wired backwards.  

Peter  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Matt Reeves

 Sent: Saturday, 8 September 2007 10:12 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: AeroElectric-List: How to check an alternator??  

Okay, I wired my ammeter backwards and here's what happens.  

I start the plane and the ammeter is on the positive side slightly.  

I turn on NAV lights, strobe lights, landing lights and the ammeter goes MORE positive and stays there and the voltage goes from 15 to right around 14.   Turn off everything, the voltage goes to just under 15 and ammeter goes to zero.  

So I don't think my ammeter was wired backwards.  

It appears my alternator is charging normally but I think my ammeter needs to see a therapist.  

Matt  

 "Robert L. Nuckolls, III" <nuckollsr(at)cox.net> wrote:  

  [quote]  

--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" 

 At 04:30 AM 9/2/2007 -0700, you wrote:

 >Hi Bob !!

 >

 >

 >Thanks for the help and suggestions !! I really appreciate you and all I 

 >learn from you.

 >

 >So, I did exactly as you said, and you are 100% correct. I left on a 

 >bunch of stuff for about 10 minutes, then started the plane and 

 >immediately noticed the ammeter was slightly on the negative side, maybe 

 >reading about 4 negative amps. The voltage read just under 15 volts - 

 >say 14.7 the whole time and stays there but within about 3 minutes, the 

 >ammeter came back up to zero and stayed there.

 >

 >I wired the ammeter and external shunt as per Van's Aircraft instructions 

 >and my brother Danny (which you've all heard from many times) says there 

 >are 2 other ways (according to Dynon) to wire the ammeter which I might do.

 >

 >I'm not sure of the best or correct way to wire the ammeter    	  Quote: 	
		    http://www.matronics.com/Navigator?AeroElectric-List 	
0 	  Quote: 	

1 	  Quote: 	

2 	  Quote: 	

3 	  Quote: 	

4[b]

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