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Sea Frog 11-06-2018 02:20

Problem installing Sterling Pro Reg D alt controller
Hello folks,

I have a problem here :) I have Sterling ProReg D that I want to install to get max out of my old Lucas alternator. The problem is that I can't figure out how to, so any input from those who know Sterling is appreciated.

The manual is more or less clear in how to choose pos or neg type of field in modern alternators, however, mine is older type that came with Perkins 4.236 and it has an external regulator driving field circuit. Sterling manual said to check a voltage between alt neg and both field inputs, and there are only 2 possibilities described there one for neg field (14 volts on one leg and 2-12 volts on the other) and one for a positive field (2-10 volts on one leg and 0 on the other).

In my case, there is 13 volts on one leg of field input and 0.5 on the other, if measured between the leg and alternator's neg output. However if you measure between legs and boat's ground, you get 9 and something on one leg and -2.5v on the other, which means that alternator's negative output is offset to boat's negative.

So it would look like this is a positive field, but I am puzzled about the offset. There should be 0 on the other leg, and it should be connected to alt's negative. But it isn't the case... Sterling manual has no info about what to do in this case. I tried emailing sterling but they never bothered to reply (like before, for some reason none of my previous emails have been answered).

So, I wonder what should I do in my case. Sure I would love to replace the alt but just can't do it right now and I am limited to this one. Any help would be welcomed!

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