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Low Voltage Light Flashing

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dbentley(at)fuse.net
Guest

Posted: Mon May 07, 2007 5:07 pm Post subject: Low Voltage Light Flashing

Bob,  

   

I need some advice.  I have a B&C L-60 alternator on my RV6.  I also have the B&C LR3C-14 voltage regulator.  They both have about 3 years of flight time, 225 hrs, trouble free.  On a flight tonight, the low voltage light came on and stayed flashing.  The panel gages show I’ve got 12.6 volts and 0 amps – nothing charging the battery.  After shutdown, I’ve checked fuses, and connectors and found nothing wrong.  With the engine shut down and the Master and Alternator switches on, I have 12 volts out at the alternator wire “B” (output), and 1.75 volts at the field connector to the alternator.    

   

I’ve pulled the alternator off, assuming I need to send it back to B&C.  Any suggestions before I do so?  

   

Thanks  

   

Duane Bentley  

   

RV6  

N515DB  

   

West Chester, OH  

        [quote][b]

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nuckollsr(at)cox.net
Guest

Posted: Mon May 07, 2007 5:34 pm Post subject: Low Voltage Light Flashing

At 09:06 PM 5/7/2007 -0500, you wrote:



 	  Quote: 	
		  Bob,



I need some advice.  I have a B&C L-60 alternator on my RV6.  I also have 

the B&C LR3C-14 voltage regulator.  They both have about 3 years of flight 

time, 225 hrs, trouble free.  On a flight tonight, the low voltage light 

came on and stayed flashing.  The panel gages show I ve got 12.6 volts and 

0 amps nothing charging the battery.  After shutdown, I ve checked fuses, 

and connectors and found nothing wrong.  With the engine shut down and the 

Master and Alternator switches on, I have 12 volts out at the alternator 

wire B (output), and 1.75 volts at the field connector to the alternator.



I ve pulled the alternator off, assuming I need to send it back to 

B&C.  Any suggestions before I do so?


	


    Sure, send the regulator back. The data you've supplied suggests

    that the alternator is probably okay and the regulator has failed.



    Bob . . .

        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

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dbentley(at)fuse.net
Guest

Posted: Tue May 08, 2007 4:02 pm Post subject: Low Voltage Light Flashing

Situation corrected.  

   

I contacted B&C this morning and talked to Tim Hedding.  He didn’t think either the alternator or regulator were defective and sent me to the troubleshooting guide for the LR3C.  Working through the steps under the panel, I traced it down to a blown fuse in the power line to the alt. field, (pin 6) of the regulator.  I had put in a 5 amp fuse instead of a breaker and missed this fuse in my check last night.  Before installing another one, I ohmed the 2-10 battery/alternator switch but found no shorts.  The rest of the troubleshoot guide was followed and all checked out.  I restarted the plane and the system charges correctly.  

   

I call Tim back and said I couldn’t find the short but would replace the switch as a precaution.  Tim suggested it was unlikely to be a switch problem and that I may have had a temporary over voltage, which blew the 5 amp fuse and shut the alternator down.  He suggested I put in a circuit breaker and check for conditions that may have caused the event, which I will do.  

   

Duane Bentley  

RV6 N515DB  

255 hrs.  

   

   

        [quote][b]

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nuckollsr(at)cox.net
Guest

Posted: Wed May 09, 2007 7:16 am Post subject: Low Voltage Light Flashing

At 08:02 PM 5/8/2007 -0500, you wrote:



 	  Quote: 	
		  Situation corrected.



I contacted B&C this morning and talked to Tim Hedding.  He didn t think 

either the alternator or regulator were defective and sent me to the 

troubleshooting guide for the LR3C.  Working through the steps under the 

panel, I traced it down to a blown fuse in the power line to the alt. 

field, (pin 6) of the regulator.  I had put in a 5 amp fuse instead of a 

breaker and missed this fuse in my check last night.  Before installing 

another one, I ohmed the 2-10 battery/alternator switch but found no 

shorts.  The rest of the troubleshoot guide was followed and all checked 

out.  I restarted the plane and the system charges correctly.



I call Tim back and said I couldn t find the short but would replace the 

switch as a precaution.  Tim suggested it was unlikely to be a switch 

problem and that I may have had a temporary over voltage, which blew the 5 

amp fuse and shut the alternator down.  He suggested I put in a circuit 

breaker and check for conditions that may have caused the event, which I 

will do.


	




   ???? Interesting! I'm wondering how you got a the votlage

   measurement on the alternator field terminal. I'll need to

   study the LR-3 schematic again and see where the "sneak path"

   exists to bias up the field terminal when the field supply

   lead is open.  In any case, Mr. Hedding is in the best possible

   position to know and he's obviously fed you good data.



   This brings up another point about the Z-figures. The

   circuit breaker shown on the drawings where the LR-3

   is featured has a specific reason for being there even

   if the rest of the airplane is protected with fuses.

   When considering a departure from what's illustrated,

   it's always a good idea to get on the List and make

   sure that you're not overlooking something.



   I'm pleased that you dodged a $time$ wasting experience

   in getting this problem resolved. I learned something

   too that needs to be researched and understood. Thanks

   for posting this to the List.



   Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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