VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #1  
Old 01-09-2022, 01:11 PM
cdeggz cdeggz is offline
 
Join Date: Jun 2021
Location: Campbell, CA
Posts: 65
Default Alternator failure, canít find cause.

It seems my backup alternator has (or wiring or regulator) has failed. Itís a 40amp B&C with LR3C regulator.

Alternator one shows 14 V and current flow. Alt two instead makes the bus voltage drop to 12V and no current.

I have gone through the entire B&C troubleshooting guide and find no issue.
Oh
I callled B&C tech support and they are stumped. Alternator has been on the engine for 200 hours and used hardly ever (checks mostly).

Hereís what I have checked so far:
Battery to pin 7: .2 ohms
Battery to engine case : .4 ohms
Master on (primary battery) bus voltage: 12V
Pin3 voltage: 11.93 volts
Pin 6: 11.76V
Pin 4: 10.53V
Alternator field resistance: 7 ohms
Field voltage 10.5V
B-lead: 11.98 volts

Yesterday I did an engine run while checking voltage at B lead and around the fuse and shut, all showed battery voltage (12V)

I made sure the alternator turns inside when I move the prop.

Any other ideas?

-Craig
__________________
Dues Paid September 2021
Reply With Quote
  #2  
Old 01-09-2022, 02:47 PM
rv8ch's Avatar
rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGY
Posts: 4,639
Default

Quote:
Originally Posted by cdeggz View Post
...
Any other ideas?
...
Hi Craig, between this and your issue with starting, I think you need to get a second pair of eyes on your wiring. Is there a nearby EAA chapter that might have a Bob Nuckolls disciple that might be able to come over and have a look?
__________________
Mickey Coggins
Fresh Ukraine update from RV-6 owner Alex 6 May 2022!
http://www.rv8.ch/help-people-in-ukraine/
"Hello, world!"
Reply With Quote
  #3  
Old 01-09-2022, 03:02 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,613
Default

You do know that vacuum pad alt wonít produce anything below around 2k rpm right?
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags, MTV-9 prop
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
Reply With Quote
  #4  
Old 01-09-2022, 03:51 PM
N49ex N49ex is offline
 
Join Date: Apr 2015
Location: Wheaton, Illinois
Posts: 160
Default Alternator failure, canít find cause.

If you do really see field voltage, AND you are spinning it at a reasonable RPM (not sure 2000 is actually required, mine puts out well below that), then it's time to suspect an alternator internal problem. At that point I would take it off the engine (yes, that lower left nut is no fun, but if you have torched a wrench into the right shape to reach it, it's not too bad...). On the bench, adapt a 12 point socket or a short piece of stiff hose with the right inner diameter and reducers to be able to drive he spline (with care, not to damage it) with an electric drill, feed the field from a DC power supply and vary it from 0 to something less than 12V with a load, say with some 12V light bulbs and see what you get. If the way you measured it in place is correct, then it probably won't put out on the bench either.

You could do the same test on the plane, disconnecting the output and field, essentially taking the regulator out of the picture and forcing the field with a power supply and putting on your own non-battery load. Since you do measure a field resistance, it seems ok, so the only other possibility is a broken internal connection to the output or from the stator windings to the rectifiers. Rectifier failure is unlikely, as multiple diodes would need to be open...

Good luck!
Reply With Quote
  #5  
Old 01-09-2022, 04:10 PM
Avanza Avanza is offline
 
Join Date: Jul 2020
Location: Vastervik Sweden
Posts: 139
Smile Regulator LR3C

Please note that the LR3C regulator is intended for Primary Alternator, not for the Standby Alternator. The regulator for the standby should be SB1B.
The voltage setting on Primary Regulator is 14,4 V and 13,0 V for Standby.
If the system Voltage reads below 13,0 V the Standby Alternator is activated.
You can find B/C documents here.
https://bandc.com/reference-library/

Good Luck
Reply With Quote
  #6  
Old 01-09-2022, 04:29 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 3,600
Default

I assume this is a new issue, as this alternator did work at some point. Did you look to see if the drive gear is still intact?

Carl
Reply With Quote
  #7  
Old 01-09-2022, 06:18 PM
johnbright's Avatar
johnbright johnbright is offline
 
Join Date: Aug 2010
Location: Newport News, Va
Posts: 436
Default vacuum pad alternator output

I made a summary of vacuum pad alternator current output from the spec sheets, ref attached image.
Attached Thumbnails
Click image for larger version

Name:	2022-05-06_17-59-49.jpg
Views:	5
Size:	338.2 KB
ID:	25507  
__________________
John Bright, RV-6A, N1921R, at FWF
O-360, 8.5:1, vert sump, dual SDS EFI EM-5-F
Z101 as a template, links

Last edited by johnbright : 05-06-2022 at 04:04 PM.
Reply With Quote
  #8  
Old 01-09-2022, 06:43 PM
johnbright's Avatar
johnbright johnbright is offline
 
Join Date: Aug 2010
Location: Newport News, Va
Posts: 436
Default LR3 as backup regulator.

I know it's thread drift but some clarification.

Be aware the setpoints of both the LR3 and SB1 regulators are field adjustable.

Bob Nuckolls does not recommend SB1 "for simple dual alternator installations". There's nothing wrong with using it but voltage sag is a better indicator of overload than the hall sensor and lamp.

A Bob Nuckolls quote:

=====================================

Posted on Aeroelectric List Mon Sep 24, 2018
.
.

The stand-by versions of the alternator controller are not recommended (by Bob) for simple dual alternator installations where the auto-switch feature is not necessary... this was a 'bell-n-whistle' aimed primarily at the STC market for TC aircraft that were receiving the pad driven, aux alternators.

Yeah, 13.0V is a bit too low . . . 13.5 is better. Will talk with B&C about this.
.
.

Bob . . .

======================================
__________________
John Bright, RV-6A, N1921R, at FWF
O-360, 8.5:1, vert sump, dual SDS EFI EM-5-F
Z101 as a template, links

Last edited by johnbright : 01-11-2022 at 07:32 PM.
Reply With Quote
  #9  
Old 01-09-2022, 07:56 PM
cdeggz cdeggz is offline
 
Join Date: Jun 2021
Location: Campbell, CA
Posts: 65
Default

Mickey, that will be the next step post-omicron if none of the ideas below work out for me.

Walt, I did not know 2k was the lower limit, but I have been doing my testing at cruise.

N49ex, yeah I was hoping to avoid pulling the alternator but it sounds like reality is setting in. Thanks for all the tips. Very helpful!

Avanza, thank you. I'll double check and make sure I got the right number. It's a simple dual alternator setup. Both connected to the main bus and individually activated using switches on the panel.

Carl, yes it's a new issue. I can see the alternator innards spinning when I turn the prop. Looks like I'll be pulling the alternator next for a better look.

John, thanks for the data and insight. This could help with troubleshooting.

You all are wonderful, thank you!
__________________
Dues Paid September 2021
Reply With Quote
  #10  
Old 01-09-2022, 08:02 PM
togaflyer togaflyer is offline
 
Join Date: Apr 2013
Location: Fl/Ga
Posts: 824
Default

Did you pull the plug from your alternator and check to verify your getting 11.5 is volts at the plug. Just insure power is getting from the switch and/or breaker to the alternator.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 05:44 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.