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B and C standby alternator not alternating i.e. broken


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My Ovation has a BC410-1 standby alternator which looks like it was installed when the TKS system was installed.  I did my semi-occasional test of it and doesn’t work.

The annunciation panel light didn’t illuminate, bulb works on test, and the amp meter continues to show negative amps.  I tried different RPMs, etc.  there really isn’t much to experiment with for diagnosing. 

Documentation in POH and the STC’s is sparse.  Online research from their web site also sparse.  Does it have its own voltage regulator?  So many questions so a logical process can be started to diagnose it.  I have repair and parts manuals, but nothing there.  

Any advise appreciated.  I will contact factory on Tuesday and see what they can provide.

thank you and stay safe.

Mark

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Mark,

They are two different alternators...

The voltage regulator is probably a single 2 in 1 box...

Typically the small alternator mounts on the old vac pump pad...

The usual trouble shooting applies... verify all wires are connected, not broken or frayed...

There is contact info for B&C around here somewhere...

There also may be discussions regarding where to get the VR OH’d...

PP thoughts only, not a mechanic...

Best regards,

-a-

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I would check the drive spline. They are prone to failure due to being  made from plastic and meant to break before they can do any damage to the accessory case of the engine.  If that’s the case it’s a cheap and easy fix.  I used to carry around a spare drive spline in my previous airplane that had that as the main alternator.  If that’s not it, B&C has a good troubleshooting guide on their website and great customer service if you give them a call. 

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I am pretty sure it is not the spline, I can move the prop and see movement inside the alternator.  

I turn the standby switch on and the annunciator light doesn’t come on....what is the wizardry and logic?  I am guessing there is a second voltage regulator behind the panel, but I don’t know.  The online material is lacking.  

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Attached is a schematic of a SIMILAR installation using the B&C 20 amp alternator: 1037260707_StandbyAltSchematicCrop.thumb.jpg.c7b23e67c899656e2ecf38f84b81878f.jpg

In 2016 I had a similar problem to what you describe.  The standby alternator was turning but there was no output.

I found that the field wire at "F" was broken.  I also found a diode from "F" to ground, reverse polarity protection apparently, not shown on the schematic.  It looked like this:1978487163_StandbyAltSchematicASFOUNDCrop.thumb.jpg.4e519995e84cc4c5e81f8a165b6e12c9.jpg

 

After repairing the wire(s) to "F" the alternator was OK again.  

B&C suggested upgrade to the newer style drive spline, which I did, too.

 

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the regulator should be mounted on the passenger side foot well under the center stack. 

There are two relays that switch the Stby Alt into the circuit, they are mounted to the bottom of the circuit breaker panel. 

B & C has a troubleshooting guide you can download from their site. 

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When mine failed we found the field terminal bad. Replaced that and things work great. Take off the connector and check out the terminal, I think they go bad early and often as they sell the replacement. connector with wire on the B&C website. In my case the IA simply replaced the spade terminal within the connector. There is also a trouble shooting routine on the B&C website. You could use the one from the Mooney manual, but it is simply a cut and paste of the B&C procedure.

 

 

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6 hours ago, Mark89114 said:

I am pretty sure it is not the spline, I can move the prop and see movement inside the alternator.  

I turn the standby switch on and the annunciator light doesn’t come on....what is the wizardry and logic?  I am guessing there is a second voltage regulator behind the panel, but I don’t know.  The online material is lacking.  

Agree with @bfreelove.  The spline is most likely the culprit based on its tendency to shear over time.  I have a spare one where I’m at down here in TX.  Say the word...

Steve

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I am pretty sure i can see the armature moving inside the alternator, so I don't believe that is the issue.  Per other reccomended troubleshooting from above, to check field wires on back of alternator.....well it appears the SOB's screws are metric......so delay with that.  I found the troubleshooting guide on the B&C website, previously didnt know what voltage regulator to look for so now I have that document.....next problem is to find the VR hidden behind the dash.  

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  • 1 year later...

sorry, I am terrible about responding…..don’t ever hesitate to bug me, my feelings won’t be hurt.

summary, a well known MSC was asked to fix it, they responded they did and tightened the field connector and tested good….well that was BS.  Ended up having my local mechanic go through it and finding a true expert.  The spline wasn’t the issue, the VR wasn’t the issue, the output from stby alternator was also outputting properly.  The issue was 2 wires buried deep behind the CB panel were not attached.  These wires connect to the Mooney relays for providing power to the emergency bus items and the notification on the annunciator panel.  We were not getting power to the emer alt switch which was a clue to one of the problems.  My mechanic stuck a borescope down into the bowels of the CB panel and discovered these beauties. The issue is accessibility, required dissasembly of large portions of the CB panel to gain access….haven’t received bill yet….wires reattached and now the system works like designed.
 

I assume somebody is still having a problem with the system not powering the bus.  I would follow the B&C checklist and eliminate their system as the problem, all of their components are easy to access and diagnose, the complexity becomes the connection to the mooney itself.  I have the diagrams for the mooney installation if anybody wants a copy.  If anybody wants more info, let me know and I will provide my cell number.  I am not a mechanic….but I do lots of work running a factory and keeping all my toys running.

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Fantastic Follow-up Mark!

Kind of scary knowing that an emergency bus doesn’t get powered by the back-up alternator before and after visiting an MSC…. :)

Is that weld marks where the wires were trying to glue themselves to something?

Thanks for sharing the details and pics…

Best regards,

-a-

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