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alternator voltage drop

Jake14

Well Known Member
Just noticed this morning that my bus voltage with the engine running was 13.8 throughout the 1-hr flight. It's always been 14.3 - 14.4 for the 650 hours since new

Plane Power, internal regulator. Belt is tight. Is this a sign of impending failure?
should I just get a new one?
 
Take the alternator "B" lead terminals apart and clean them and reassemble.
Make sure all charging system connections are clean and tight.
 
went to check the connections like you said but it looks like it's throwing oil..so ordered a new one from AS $1249 with core charge.. !!!

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There is no oil in an alternator

went to check the connections like you said but it looks like it's throwing oil..so ordered a new one from AS $1249 with core charge.. !!!

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IMHO... That is engine oil. The alternator brushes may be soaked in this oil, and might need a cleaning or replacement. Do not throw that alternator out, it may still have some life left.

You will need to hunt down the oil leak. If not fixed, the leak will possibly damage your new alternator in short order.
 
fixed the photo

As just said, no oil in Alternator.
 

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Hmmm..of course ...I guess my first thought was that a bad bearing was causing the mess, but obviously not the case..thanks for the responses :eek:
 
Feel the back side of the ring gear/flywheel, if there is oil, it will be your front crank seal leaking.
 
Wow $1249

Really glad I'm using a Autozone Part# 14824 $80 alternator.
13 yrs and 1300 hrs on the first one. Over 150 hrs so far on the second one.
 
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went to check the connections like you said but it looks like it's throwing oil..so ordered a new one from AS $1249 with core charge.. !!!

View attachment 27820

You do know that a brand new alternator kit at Vans costs "only" 925$

https://store.vansaircraft.com/plane-power-60a-alternator-kit-es-alternator-deluxe.html

and you can keep the core. You also will get a belt, brackets and other stuff you won't need but still 324$ cheaper then going to Plane and Power and getting the "deal" with core credit ... .


Oliver
 
My IO-360 had a similar (but smaller) leak when new, but has since (180 hours) disappeared. That leads me to believe it was a front main seal settling in...

Just a guess, but mine stopped.
 
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My IO-360 had a similar (but smaller) leak when new, but has since (180 hours) disappeared. That leads me to believe it was a front main seal settling in...

Just a guess, but mine stopped.

Exactly the same here. I thought the leak stopped because I started using 15W50 oil, or because I started using Camguard. I almost pulled the prop - happy I didn't.
 
Oil Leak/Alternator

Check torque on the two through bolts on the nose of the engine case. I find them loose all the time on customers planes.
Those 60 amp Plane Power alts. are known to break the stator wires where they attach to the diode assy. especially if the prop isn't balanced. I've replaced several over the years.
 
AutoZone Alt's

I'm with BobbyHester on this one. I LOVE my alt from the local auto parts aviation section. Less than $100. I had one of theirs fail after a couple years and they replaced it free! The other good... no GREAT thing is that no matter where I am I can likely get one... even on a Sunday! I'm happy. I will add this. I am VFR only. If I was flying around hard IFR I would likely spend the money and time for an aviation certified alternator.
 
Thanks for all the tips/suggestions, very helpful. Update is, I returned the AS alternator and bought the brush kit for the PP 99-1012 (internally-regulated) alternator. Installed it and the voltage went up to about 13.8 to 13.9...didn't seem good enough. Bought a new alternator from Van's as suggested and now the voltage is at 14.0 - 14.1 (voltage measured at the EFIS, AV-30 and USB outlets all correspond)

Still not the 14.3 or so I got in the first 5 years of flying the aircraft.. checking for loose wires but haven't found anything. Maybe 14.0 is enough to keep the PC680 charged? or should I look further?
 
Thanks for all the tips/suggestions, very helpful. Update is, I returned the AS alternator and bought the brush kit for the PP 99-1012 (internally-regulated) alternator. Installed it and the voltage went up to about 13.8 to 13.9...didn't seem good enough. Bought a new alternator from Van's as suggested and now the voltage is at 14.0 - 14.1 (voltage measured at the EFIS, AV-30 and USB outlets all correspond)

Still not the 14.3 or so I got in the first 5 years of flying the aircraft.. checking for loose wires but haven't found anything. Maybe 14.0 is enough to keep the PC680 charged? or should I look further?

14.0 - 14.1 is what I get with my PP alternator. I have an EarthX 680c, and this is in the range they recommend (13.8 - 14.6 volts). I guess it's a similar range for the PC680, and should be fine.
 
Thanks for all the tips/suggestions, very helpful. Update is, I returned the AS alternator and bought the brush kit for the PP 99-1012 (internally-regulated) alternator. Installed it and the voltage went up to about 13.8 to 13.9...didn't seem good enough. Bought a new alternator from Van's as suggested and now the voltage is at 14.0 - 14.1 (voltage measured at the EFIS, AV-30 and USB outlets all correspond)

Still not the 14.3 or so I got in the first 5 years of flying the aircraft.. checking for loose wires but haven't found anything. Maybe 14.0 is enough to keep the PC680 charged? or should I look further?

I would look for resistance on the wiring that is feeding your voltage instrument or any wiring between it and the Alt. Any resistance here will under report the actual voltage being produced by the Alt. You can test this by putting your VOM directly on the battery with the engine running. This will give an idea of the actual alternator output voltage, unless there is resistance on the B lead to battery wire. The VOM on the B lead will give true output readings, but will need jumper wires as that is pretty close to the spinning prop.

Larry
 
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Circuit Breaker??

I've got a 60 amp breaker in the B lead Circuit. My voltage dropped from 14.3 to 13.7 one day and never went back - we isolated the breaker and found the voltage drop across it. 16 years and 2600 hrs - I was not too upset - they are $15 at Spruce.

New breaker is on the way - worth checking if you have one in the circuit.

Update - this is pretty much what Larry just said above......


Thanks for all the tips/suggestions, very helpful. Update is, I returned the AS alternator and bought the brush kit for the PP 99-1012 (internally-regulated) alternator. Installed it and the voltage went up to about 13.8 to 13.9...didn't seem good enough. Bought a new alternator from Van's as suggested and now the voltage is at 14.0 - 14.1 (voltage measured at the EFIS, AV-30 and USB outlets all correspond)

Still not the 14.3 or so I got in the first 5 years of flying the aircraft.. checking for loose wires but haven't found anything. Maybe 14.0 is enough to keep the PC680 charged? or should I look further?
 
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