started having problems with my isolator or alternator I have over 16 volts going to the coach auxiliaries batteries and under 12 volts going to the coach starting batteries if I use the the Boost switch I have 14.2 at both sets I have a good ground on alternator and isolator 12 volts at ignition side of alternator voltage at the alternator output over 15 volts plus. looks to me like it's the isolator ,this started yesterday. this morning I I started it up it was charging perfectly on both set ran it for an hour shut it down started it back up and the problem was back and is still there any suggestion it has a 4 stud isolator one wire goes to the back of alternator a small 12 gauge wire and the other 3 wire about 4 gauge main wire output on alternator and other two goes to each battery set there is one thing I find odd on the ignition wire that what I'm calling it I didn't Reese trace it out. it is live all the time key on or off .
I also had it plugged in to shore power I can see that Would interfering with the battery if coach was running for over an hr or so would the alternator and the inverter working at the same time be hard on the isolator
Rick, this looks like the isolator is on its way out. Time for a new diode based isolator like you have or a zero voltage drop isolator or an automatic combiner or voltage sensitive relay.
The first two charge both the house and start batteries while driving. The second two also do that and while charging from the inverter/charger or solar will do both depending on voltages.
Best done sooner than later.
The wire that is hot all the time should be the sense wire. The ignition wire is only hot with the key on.
Will do some research on the last two
Read an article one time, don't remember where, that said the isolator was good for 16 to 20 years under normal use. Don't know exactly what that means.... Sounds like it may be time for a replacement.