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  #1  
Old 08-23-2022, 10:38 AM
Reaver Reaver is offline
 
Join Date: Sep 2017
Location: Palo Alto, CA
Posts: 136
Angry AOG: Possibly Dead Alternator?

Voltage slowly dropped to ~10.5V in flight, cycling alternator field circuit didn't help, currently safely on the ground in a hangar. Any troubleshooting advice would be much appreciated!

Electrical System: VPX
EFIS: Dynon Skyview
Alternator: not positive about the model but it appears to be the old Vans FWF-supplied model. It's labeled "NL" on the back, and has the same connections shown here: https://www.vansaircraft.com/wp-cont...ing_change.pdf

Debugging so far:
- With the engine running or stopped, the VPX shows zero current draw from the alternator field circuit.
- With the engine off, I get full battery voltage (12.5) on both of the vertical spades on the alternator wiring plug (reference PDF above for image).
- Immediately after turning off the alternator circuit on the VPX, I still get 11.6V on both vertical terminals on the harness. I "hand propped" the propeller a few revolutions with the harness connected to see if there was a capacitance that might be keeping those lines energized and no change. I'll come back to the plane later to see if there's a capacitor that just needs time to discharge, but it seems strange that there would still be voltage.
- I took a hacksaw blade and placed it next to the alternator with the field engaged (engine off) but did NOT feel a magnetic pull.
- On the Alternator, I measure 10.9MOhms resistance between the two vertical spades, and open circuit between any other pair of two spades. I didn't think to check resistance to ground or the output B terminal while at the hangar, but can do so tonight if that's helpful.

Other note: I have a battery minder, so I'm able to keep it topped up and start the engine (within reason) as much as I need to for debugging.

Based on this, I'm suspecting that the alternator has indeed died and will need to be replaced, but posting here in case anyone sees something that I'm missing.

Two other questions:
- Does anybody know what model alternator Vans used to supply with the FWF kit, before the change mentioned in the PDF above, and what is currently available that is compatible (likely needing to disconnect the second vertical spade from the battery sense line as mentioned in the PDF)?
- Is this considered and internally or externally regulated alternator?

Thank you in advance!
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Last edited by Reaver : 08-23-2022 at 11:16 AM.
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  #2  
Old 08-23-2022, 10:44 AM
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BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
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Does it look like this?

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Here is one from Autozone.
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Last edited by BillL : 08-23-2022 at 10:47 AM.
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  #3  
Old 08-23-2022, 11:07 AM
Reaver Reaver is offline
 
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Yes it does look like that, thanks Bill. Do you know if I swap it out, should I disconnect the red wire as indicated in the Vans change document? Right now only blue is not connected.
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  #4  
Old 08-23-2022, 11:10 AM
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BillL BillL is offline
 
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Location: Central IL
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Quote:
Originally Posted by Reaver View Post
Yes it does look like that, thanks Bill. Do you know if I swap it out, should I disconnect the red wire as indicated in the Vans change document? Right now only blue is not connected.
I hesitate to recommend not knowing what each does without research. Maybe now we know the part, people more familiar can say. Many have used this alternator.

edit: I suspect you would wire the same, some alternators use a battery voltage to trigger the field via the voltage regulator.

I agree it is odd to have that voltage when master is off, but again, I don't know this circuit well.

Here is a thread talking about it. https://vansairforce.net/community/s...d.php?t=181869
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Last edited by BillL : 08-23-2022 at 11:19 AM.
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  #5  
Old 08-23-2022, 12:10 PM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Quote:
Originally Posted by Reaver View Post
Based on this, I'm suspecting that the alternator has indeed died and will need to be replaced, but posting here in case anyone sees something that I'm missing.

Two other questions:
- Does anybody know what model alternator Vans used to supply with the FWF kit, before the change mentioned in the PDF above, and what is currently available that is compatible (likely needing to disconnect the second vertical spade from the battery sense line as mentioned in the PDF)?
- Is this considered and internally or externally regulated alternator?

Thank you in advance!
It is either a bad alternator, a bad voltage regulator (inside the Alt) or a wiring issue. Likely the Alt is putting a deep load on the bus due to failure, so no surprise that it is dropping to 10.5 volts once in the circuit. It looks like a plane power internally regulated alternator, but can't say for sure, but PDF implies this (60 amps and no field connection). This can be replaced with an automotive Alt (internally regulated) to get you in the air faster and many, myself included, would argue that it will last twice as long at 1/10 the price. I use externally regulated, so can't offer a part number, but a quick search will show several options.

Larry
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Last edited by lr172 : 08-23-2022 at 12:18 PM.
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  #6  
Old 08-23-2022, 12:26 PM
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Walt Walt is offline
 
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Location: Dallas/Ft Worth, TX
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Looks like it... PN shown, prob autozone or Orielly has one.
You can have this one if you come get it.
(It's a POS, that's why it is getting replaced with B&C along with a new panel)
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Last edited by Walt : 08-23-2022 at 02:50 PM.
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  #7  
Old 08-23-2022, 12:50 PM
jclark jclark is offline
 
Join Date: Jan 2005
Location: Columbia, SC
Posts: 969
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Quote:
Originally Posted by lr172 View Post
It is either a bad alternator, a bad voltage regulator (inside the Alt) or a wiring issue. Likely the Alt is putting a deep load on the bus due to failure, so no surprise that it is dropping to 10.5 volts once in the circuit. It looks like a plane power internally regulated alternator, but can't say for sure, but PDF implies this (60 amps and no field connection). This can be replaced with an automotive Alt (internally regulated) to get you in the air faster and many, myself included, would argue that it will last twice as long at 1/10 the price. I use externally regulated, so can't offer a part number, but a quick search will show several options.

Larry
If the "Lester" number (I think that's the name) of 14684 is correct, then this is not a Plane Power alternator.

Several friends have used them (and made use of the limited "lifetime warranty" to get replacements on the road.)

[I have used them along with Plane Power and B&C].

Available at most parts stores for around $150. It is internally regulated.
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  #8  
Old 08-23-2022, 04:20 PM
SPX SPX is offline
 
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Location: San Diego
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Lester Nos: 14684

The alternator you want is Used On:
(1988-87) Chevrolet Sprint 1.0L
(1995-86) Suzuki Samurai 1.3L
(1989) Suzuki Sidekick 1.3L

O'Reilly PN R111413A
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  #9  
Old 08-23-2022, 09:40 PM
A1AVIATON47 A1AVIATON47 is offline
 
Join Date: Apr 2008
Location: DEWEY AZ
Posts: 291
Default NEW ALT.

I Ran into this prob. when doing an cond. insp on a rv6 , bad alt , took it to repair shop they rebuilt it asked were is the cooling fan, not there, cowl would not fit with a fan on alt. It over heated with no cooling fan, put rebuilt alt on eng.
owner did not want to spend the money to redo it. Take alt. to gen shop have them check it. see what they say, I did not see any coolin fans on alt in pictures
good luck
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  #10  
Old 08-23-2022, 11:36 PM
JDeanda JDeanda is offline
 
Join Date: Apr 2013
Location: Ventura, CA
Posts: 364
Default Will They Test It For you?

If it's an AutoZone or O'Reilly alternator, will they test it for you in the store? We have one of each in our one-horse town and they both test alternators and starters right in the store for free. Not that you always get a good diagnosis. Our RV-6 came with a no name, no numbers alternator with some nondescript external regulator. When it's output dropped and didn't keep up with demand, the local auto electric wizard tested both and declared they were OK. I installed an early internally regulated Plane Power alternator and it's been perfect for about 500 hours and 6 or so years.
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