Helping Dave with a house battery charging problem,alternator putting out 13.7 volts,all connections and batteries good,have 13.7
going into isolator,13.7 going to start batteries,12.3 going to house batteries,house batteries are 1 year old...

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What kind of isolator:

Diode based?  If so, what are voltage readings at center lug and the two outer lugs with engine around 1.100 RPM?

Solenoid/relay based?

Diode based,looks like a Cole Hearse but no label,13.7 at center,13.7 at start battery,12.3 at house battery post,is 3 post isolator.

Indeed, bad isolator.

But a little confusing: Reading on center lug (direct connection to alternator B+ terminal should be about .7 VDC higher than the two readings on the outer lugs (one to each battery bank).  That .7 VDC loss is turned on to...

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Will remeasure the voltage,thanks,got the message.

Thank you Brett & Dave! It was definitely the isolator, will replace next week.

Dave,

If you need to travel before replacing it, let us know.  Several easy work arounds for a failed isolator.

Dave,

If you need to travel before replacing it, let us know.  Several easy work arounds for a failed isolator.

No hurry, we're in Arizona till mid March. I was running the generator to keep...

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