I have a 2016 SMB Sprinter buildout with a Nations secondary alternator charging the house batteries in addition to a couple of solar panels. In 40k miles, I've had three of these alternators fail due to a corroded power stud. In my experience this seems like a far to common issue. If anyone else is seeing this as well, please chime in, particularly if you have found a solution.
Have you tried coating it with dielectric grease. I believe the second alternator is mounted pretty low correct? Does your second alternator have an external regulator, are your house batteries lithium?
-greg
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-greg
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"Goldilocks" 2020 Ford Transit High Roof Extended 3.5 EcoBoost AWD Homebuilt