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-content/uploads/2019/01/60amp_alternator_wiring_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!
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-content/uploads/2019/01/60amp_alternator_wiring_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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