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Hi all, Been boating for around 6 months all been going well, until a week ago, when I notices the Domestic batteries where not getting charged. Running a Beta 38 with dual alternators and twobattery sets, single starter and four domestic batteries, these are not linked in any way. The started runner circuit seems to run OK. So I did the following: Checked alternator output, 10v - so not good, so I ordered a new alternator 100Amp 14.1V. This also was confusing as I would of expected to at least see the battery voltage across the alternator. After replacement, still only getting 10V (slight panic as the new alternator was £150) Got on blog and someone mentioned isolator switches, but both mine where replaced when I changed to position of the isolator switches about 6 months ago, and they where not cheap !!!! As a test, I bypassed the isolator on the domestic side and now get 12.8V from alternator (was expection 14.xx) seems like battery voltage......Oh dear so the alternator seems to be working but not at the correct voltage - did it get fried due to a faulty isolator ? the batteries are getting some change, but not whats needed to get them to a fully charged situation. I check both isolators, ie domestic and started, and both seem to be intermittent, sometimes they work, other times not, and pushing the key in seems to affect their operation. Seems like both need to be replaced. Just got back from boat, slighty frustrated, but slighty happy about the fact that the isolator switches seem to be the issue, but worried about alternator output. Questions: Did I fry the alternator, due to a faulty isolator switch, I have the original which I have go repaired and was going to use as spare Why only 12.8V. is this linked to above and/ is this the battery voltage showing Any suggestions on a good make of isolator hope that makes sense. Kev