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Alternator Ground

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David Lamphere

Joined: 20 Oct 2019
Posts: 19
Location: Culpeper, Virginia

Posted: Thu Jan 14, 2021 2:07 am Post subject: Alternator Ground

That’s one I actually think I can answer!

The ground is through the alternator’s chassis, mount, engine case and ground strap from engine to firewall ground terminal.



That’s why having a good ground connection to the engine is important.



Dave

On Jan 13, 2021, at 10:26 PM, Dan <limadelta(at)gmail.com> wrote:



I have a Continental IO 550 with a Kelly 70 amp 12 volt alternator.  The wiring diagram shows two field terminal posts (F1 and F2), a positive terminal, and an "AUX" terminal.  It does not show a ground.  Any idea how this alternator is supposed to be wired to ground?  See attached pic.



Thanks,

Dan

<Alternator pic.pdf>

alec(at)alecmyers.com
Guest

Posted: Thu Jan 14, 2021 4:38 am Post subject: Alternator Ground

Ground is through the metal frame of the alternator, bolted to the engine, no?



On Jan 13, 2021, at 22:32, Dan <limadelta(at)gmail.com> wrote:





I have a Continental IO 550 with a Kelly 70 amp 12 volt alternator.  The wiring diagram shows two field terminal posts (F1 and F2), a positive terminal, and an "AUX" terminal.  It does not show a ground.  Any idea how this alternator is supposed to be wired to ground?  See attached pic.



Thanks,

Dan

<Alternator pic.pdf>

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jan 14, 2021 8:16 am Post subject: Alternator Ground

At 04:03 AM 1/14/2021, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: David and Elaine Lamphere <dalamphere(at)comcast.net>



 That’s one I actually think I can answer!

 The ground is through the alternator’s chassis, mount, engine case and ground strap from engine to firewall ground terminal.



 That’s why having a good ground connection to the engine is important.



 Dave 	


   Correct. Both starter and alternator seek

   ground through their attachments to the

   engine. That fat/flexible jumper from

   crankcase to firewall ground stud is

   really important.



   Further, this alternator has a 2-terminal

   field connection. One of those terminals

   should be grounded to alternator case.



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

jluckey(at)pacbell.net
Guest

Posted: Thu Jan 14, 2021 9:34 am Post subject: Alternator Ground

Hey Bob,

I have 2 questions:

1. Is the reason that some alternators surface both ends of the field so that the end user can select either an A-Circuit or B-Circuit regulator?  (Thus giving the user more regulator choices.)

If so, then your advice:

"Further, this alternator has a 2-terminal  field connection. One of those terminals  should be grounded to alternator case. "

would only apply to an B-Circuit regulator.

2.  Is that correct?

I seem to remember working on some big Leece Neville alternators (read big & expensive) where both sides of the field were available but don't remember what regulators were used (that was decades ago).

3. Are you aware of any automotive vehicles where they used and alternator with both side of the field exposed?  ( I imagine not since in the automotive world it's all about cost)





-Jeff

                  

                                                                    On Thursday, January 14, 2021, 08:25:35 AM PST, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:                 

                 



                 



                   At 04:03 AM 1/14/2021, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: David and Elaine Lamphere <dalamphere(at)comcast.net>



 Thatâ€™s one I actually think I can answer!

 The ground is through the alternatorâ€™s chassis, mount, engine case and ground strap from engine to firewall ground terminal.



 Thatâ€™s why having a good ground connection to the engine is important.



 Dave 	


   Correct. Both starter and alternator seek

   ground through their attachments to the

   engine. That fat/flexible jumper from

   crankcase to firewall ground stud is

   really important.



   Further, this alternator has a 2-terminal

   field connection. One of those terminals

   should be grounded to alternator case.



 

 

    Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Thu Jan 14, 2021 1:22 pm Post subject: Re: Alternator Ground

Hi Group I helped a friend a number of years ago chase down cause of a flaky alternator output on his V-Tail Bonanza. He recently had a Major. A&P changed regulator. Owner took alternator to a car parts place and had alternator tested and all was well? When I looked at alternator it looked beautiful, it was newly painted. I tried to tighten the two halves of the alternator together and things were not tremendously tight. This was after a flight when things were hot. I was able to put my thumbnail into the new paint and it was thicker than I think it should have been. I loosened halves, pulled apart enough to clean of paint between halves and re tightened. Problem was paint was insulating connection of 2 halves of alternator. Ron P.

bob.verwey(at)gmail.com
Guest

Posted: Thu Jan 14, 2021 9:49 pm Post subject: Alternator Ground

Very interesting !



On Thu, 14 Jan 2021, 23:30 rparigoris, <rparigor(at)hotmail.com (rparigor(at)hotmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com (rparigor(at)hotmail.com)>

 

 Hi Group I helped a friend a number of years ago chase down cause of a flaky alternator output on his V-Tail Bonanza. He recently had a Major. A&P changed regulator. Owner took alternator to a car parts place and had alternator tested and all was well? When I looked at alternator it looked beautiful, it was newly painted. I tried to tighten the two halves of the alternator together and things were not tremendously tight. This was after a flight when things were hot. I was able to put my thumbnail into the new paint and it was thicker than I think it should have been. I loosened halves, pulled apart enough to clean of paint between halves and re tightened. Problem was paint was insulating connection of 2 halves of alternator. Ron P.

 

 

 

 

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AdventureD

Joined: 13 Jan 2021
Posts: 16

Posted: Fri Jan 15, 2021 8:38 am Post subject: Re: Alternator Ground

[/quote]

   Correct. Both starter and alternator seek

   ground through their attachments to the

   engine. That fat/flexible jumper from

   crankcase to firewall ground stud is

   really important.



   Further, this alternator has a 2-terminal

   field connection. One of those terminals

   should be grounded to alternator case.



   Bob . . .[/quote]

Interesting.  I had simultaneously contacted Continental (It's an IO550), and they said to run a ground wire from a screw holding the (??alternator brush"") to the case.  But if the alternator is already grounded via attachment to the case, why would that be needed?  They did not mention grounding the second field terminal to the case.  So now I'm confused 



Separately, the SD20 backup alternator field also has two leads and it takes a connector that I either lost or was not supplied with the alternator.  (See attached pic).  Anyone know where I can get that two lead connector?  Maybe an auto parts shop?  And does one of those wires ground to the alternator case?

Alternator field connection.jpg

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rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Sat Jan 16, 2021 10:59 am Post subject: Re: Alternator Ground

Hi AdventureD "if the alternator is already grounded via attachment to the case, why would that be needed?" See my post on this thread about the V tail Bonanza alternator. I located a bad connection between the two halves of the alternator. Running a separate wire to ensure the back half of the alternator isn't a bad idea if you didn't want to disassemble alternator. Ron P.

rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Sat Jan 16, 2021 7:29 pm Post subject: Re: Alternator Ground

Hi AdventureD For SD20 connector: https://bandc.com/product/replacement-field-connector-for-alternators-l-40-bc410-h-bc425-1-sk35-lom30/ as far as field wires, they are to be paralleled to regulator. I have a SD20S and just twisted 2 wires together from regulator to go to both field wires. One is not a ground. You can just make a short paralleled wire as well. Here's install manual: https://bandc.com/wp-content/uploads/2018/05/install-instructions-bc410_revC.pdf As far as grounding for SD20, it's grounded by the 4 mounting nuts. I'm going the belt and suspenders route and running an extra ground from one of the screws on the brush side of case to engine ground.  Note they want you to cross tighten to 20 inch lbs, then go to 60 to 70 inch lbs. I'm going to weld up a 12 point torque adapter for my 1/4" torque wrench. Manual tells you torque value for B+ nut. Best not tighten to the old stand by of stripping and backing off 1/2 turn! Ron P.

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jan 17, 2021 10:14 am Post subject: Alternator Ground

At 09:29 PM 1/16/2021, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com>



 Hi AdventureD For SD20 connector:

   https://bandc.com/product/replacement-field-connector-for-alternators-l-40-bc410-h-bc425-1-sk35-lom30/ 

  as far as field wires, they are to be paralleled to regulator. 	


    There is only ONE wire from the field

    connector to the regulator on B&C wound-

    field alternators.



    These are automotive conversions where

    two of the original terminals on the back

    were control and warning light connections.



    The conversion process removes the stock

    regulator and they used to tie ALL pins

    of the rear end bell connector together

    such that any one would suffice as a field

    connection. The are always configured to

    operate as B-circuit fields (one brush

    grounded inside).



  	  Quote: 	
		  I have a SD20S and just twisted 2 wires together from regulator to go to

 both field wires. One is not a ground. You can just make a short paralleled

 wire as well. 	


    Twisted wires? You lost me there.



  	  Quote: 	
		   Here's install manual:  https://bandc.com/wp-content/uploads/2018/05/install-instructions-bc410_revC.pdf  	


   Okay, yeah. Instructions call for tying

   both pins in the connector together with

   a jumper at the plug . . . this is for

   redundancy in the fast-on terminals. One

   wire from alternator field to regulator

   suffices.



   I note that they recommend crimp+solder

   for applying those open barrel fast-on

   terminals. Nothing 'wrong' with that but

   if you lack confidence in the crimp

   quality of your crimp tools, review

   this document



  https://tinyurl.com/y6g6rl9f



   on page 11 we find a table of minimum

   tensile strength of various crimped

   terminals. In the 'Connection' I

   describe a po' boy's technique for

   validating crimp quality.



   Suggest you validate your wire/terminal/tool

   configurations before incorporating them

   into your airplane. The back of the SD20

   is not the ONLY place where crimp quality

   is of importance . . . soldering of qualified

   crimps is unnecessary.

 

 As far as grounding for SD20, it's grounded by the 4 mounting nuts. I'm going

  	  Quote: 	
		  the belt and suspenders route and running an extra ground from one of the

 screws on the brush side of case to engine ground. 	


   For what purpose? The resistance between

   components of the assembled case is measured

   in micro-ohms . . . a milli-ohm jumper around

   these joints is of no electrical value.



   Hedge against what other condition . . . mechanical

   looseness that disconnects the end bell from the

   rest of the alternator?  Those fasteners are

   like prop bolts and strut attachments. I.e.

   at the very bottom of risk levels in a reliability

   study.



  	  Quote: 	
		  Manual tells you torque value for B+ nut. Best not ighten to

 the old stand by of stripping and backing off 1/2 turn! 	


  Never heard of such a practice. The physics of

  achieving the required make up forces by measuring

  the tightening force on a threaded fastener

  is quite clear. Backing off any fastener after

  achieving the specified tightening torque has

  no obvious merit.



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

B&C_Alternator_Field_Connections.jpg

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user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Sun Jan 17, 2021 12:12 pm Post subject: Re: Alternator Ground

 	  Quote: 	
		  Best not tighten to the old stand by of stripping and backing off 1/2 turn! 	


Bob, I think he was joking with that sentence.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jan 17, 2021 12:35 pm Post subject: Alternator Ground

At 02:12 PM 1/17/2021, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>



 

 > Best not tighten to the old stand by of stripping and backing off 1/2 turn!



 Bob, I think he was joking with that sentence. 	


   Opps! Missed 'stripping' . . . my 9th grade

   English teacher would keep me after school

   for that one!



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Sun Jan 17, 2021 1:27 pm Post subject: Re: Alternator Ground

Hi Bob As far as twisting 2 wires together, it was just to keep them together and make them a bit stronger. I decided to use 2 wires instead of one for the field because I need to span a distance from the regulator which is in the starboard footwell to the engine and 2 wires are a bit more robust. Using 1 wire with a parallel splice is fine electrically.

As far as grounding the SD20S goes, there's a gasket installed on the vacuum pad that insulates the large surface area. That said you do have 4 lock washers and nuts attached to studs in the engine case. If you read earlier in this thread about my finding a V-Tail Bonanza alternator with poor contact between the two halves of the alternator causing problems. True it was paint at fault, but between the gasket decreasing surface area, and the fact that B&C makes a new nose for the SD20S that I'm just not certain that it has a great contact with the back half. If looks like it might be plated? Not sure if plating is conductive? Also on Rotax they tend to use Loctite on many things and I have heard that when Loctite gets old, it can cause high resistance in senders. Can that happen on studs too? Perhaps not, but I can't speak with certainty. I'm pretty certain B&C has their act together and would have addressed connection if there was a problem with ground between the case halves. A lot easier to run a 5" piece of wire to a pretty nice grounding pad nearby. Ron P.

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