Alt load imbalance

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salim
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Alt load imbalance

Post by salim »

Hello,

During a couple of recent flights, the Right Alternator load was significantly higher than the left one.
Any idea of a possible explanation ?

Thanks a lot,

Best regards,

Salim
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Davestation
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Re: Alt load imbalance

Post by Davestation »

Unless you’re in a late model NG the regulators do not parallel and the old ones aren’t even adjustable so a small split is a function of all the subtle differences between the busses and their loads. An increasing/large split can indicate an alternator on its last leg or a regulator malfunction. One simple test would be to swap the regulators around and see if it follows.
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Re: Alt load imbalance

Post by salim »

Thank you David !

The alternators are relatively new (>180h and 6 months) as are the engines. Do you confirm the regulators are not part of the engine / alternator assembly ?

Thanks a lot

Salim
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Re: Alt load imbalance

Post by Davestation »

There is no life limit on the regulators, which are mounted in the nacelles, so if the alternators are young and healthy, those would be my next line of troubleshooting.
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Re: Alt load imbalance

Post by slowbird »

Hi Salim

Did you get this fixed? We had a the same issue for the past year on a newish DA42-VI. If you turn the right Alt Off (on the ground of course), then the left picked up the load happily. So clearly the alternator is working.

In the end we have upgraded the G1000 software and that seems to have cured the fault, for now anyway.
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Re: Alt load imbalance

Post by salim »

Hi Slowbird,

On my plane as well, any alt would pick up the load happily when opposite side was turned off.

Then the issue somehow disappeared by itself...

Now both are within 2 amps so looks fine to me

Best
Salim
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Re: Alt load imbalance

Post by wolfvoador »

Item: 9 - Airworthy
Discrepancy Hours Subtotal
C/W INSTALLATION OF WI-OSB 42NG-034 IMPROVED ALTERNATOR REGULATORS.

Corrective Action
C/W DIAMOND OSB42NG-034 INSTALLED IMPROVED ALTERNATOR REGULATORS KIT P/N
OSB-42NG-034-KIT I/A/W THIS S/B AND DA-42NG MM CH 24-31, 25-10, 71-10, 81-00 AND 76-00. OPS CHECK WITH IN LIMITS.

69.55 hours $ 7,511.40

Parts
2 EA 04001 ADHESIVE: EPOXY, RED, 3.5GM, EXTRA FAST SET (P/O: 24076)
0.5 FT 1LEZ6 SPIRAL WRAP, 3/4" NATURAL COLOR, -40 TO 122F (P/O: 11766)
2 EA CS1900KIT SEALANT (P/O: 24618) (Retail Price: 27.42)
1 EA OSB-42NG-034-KIT KIT, ALTERNATOR REGULATOR (P/O: 24518)
(Retail Price: 5,106.56)

Labor: $7,511.40 Parts: $5,220.12 Shipping: $118.20 Item Subtotal: $12,849.72

Summary of my invoice to fix the issue, almost $13,000!
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Re: Alt load imbalance

Post by slowbird »

$13k to fix a warning for an alternator that is working fine and just needed and improved regulator to make the software happy. Wow!

We had a regulator swapped for a new one, but didn’t fix the issue. Next steps was upgrade the Garmin software. Now wait and see.
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Re: Alt load imbalance

Post by Davestation »

slowbird wrote:
Sat Aug 08, 2020 11:45 am
To fix a warning for an alternator that is working fine and just needed and improved regulator to make the software happy.
I don’t think that’s a fair synopsis. The alternator is not working fine, it’s offline due to a bad regulator. The fix is not to make the software happy, the fix is to make the alternators share the load equally so that one doesn’t Wear out faster or even burn up.
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Re: Alt load imbalance

Post by Soareyes »

Reactivating this thread with another report of an alternator imbalance in a nearly new, 2020 DA42.

The plane has been in the shop this time for five weeks so far, first for the oil pump replacement AD, then deciding to do the annual at the same time, then the alternator load imbalance.

The only squawk going in was the left alternator reading half of what the right one read, both on the ground and in flight. On the ground it would intermittently set off a L ALT FAIL message which resolved with a slight increase in rpm. Had been happening more frequently lately. Normal run ups. The shop waited until everything else was done before evaluating the alternators.

Premier says it needs a new current sensor, part number D4D-2466-12-00-DA40. Guess what is on back order?

In it's first year this plane has been AOG two weeks for a fuel tank leak, two more weeks for a software mystery issue, now five weeks and counting for the latest. Anybody know a source for a current sensor?
DA42-V1

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