Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 06, 2025 ...

The tech is correct when he recommends the 48162 isolator, but I think he is incorrect in saying the 48160 isolator has "failed".  It didn't fail - it was just improperly paired with the Wilson alternator.  The Wilaon 90-01-4721 alternator is a clone (or rebuilt) version of a Delco 28Si alternator.  The 28Si will not turn on unless it sees 12V on the B+ output terminal.  If this model alternator is connected directly to a battery (like when you bypassed the isolator) then it works fine.  BUT, when it is connected to the center post on the isolator, it can't see any 12V signal, because the isolator diodes prevent voltage from the battery posts getting to the center post.  So, the alternator will not turn on.  The solution, in this case, is to use a isolator that includes a separate "ignition terminal".  You connect a wire to this terminal that is hot only with ignition switch in ON position.  The "ignition terminal" on the isolator supplies the required 12V signal to the isolator alternator post, which will then tell the alternator to turn on.

I can't tell (from my search) if the Wilson 90-01-4721 alternator has a "sense" terminal.  If it DOES NOT have a sense terminal, then it will still not work correctly on your coach, even if they replace the isolator.  If it DOES have a sense terminal, then it will work.  The sense terminal on the alternator should be connected to a 12V source that is HOT all the time.

If the Wilson alternator does NOT have a "sense" terminal, then I would recommend a different replacement isolator.  The Victron ArgoFET 200-2AC has the requisite "ignition" terminal AND in contrast to diode isolators has virtually zero voltage drop between the alternator post and the battery posts.

https://www.amazon.com/Victron-Energy-Argofet-200-2-Batteries/dp/B00NT9MTMQ

https://www.amazon.com/Cole-Hersee-48162-Battery-Isolator/dp/B07BYH6Q9M

https://www.truckspring.com/products/Alternator-Wilson-180-Amp-New-28SI-Type__90-01-4721N.aspx

Thank you for the reply.  The tech's summary included this statement "the model 48162 is a 12-36 VDC 200A with a 4th leg. We would need to make and connect to an ignition circuit on the unit for proper operation with the installed alternator. "  Excuse my ignorance, but does it sound like he is referencing the sense terminal that must be connected to 12V source that must be HOT all of the time? Thanks in advance!

The way I interpret the tech's statement is he is talking about the "ignition" terminal on the 48162 isolator, saying it must be connected to a "hot with ignition ON" voltage source.  So he is correct in that statement.  However, he is not addressing the question about whether or not your Wilson alternator has a "sense" terminal.  You should ask them about this.

The reason a diode isolator will not work in the absence of a "sense" terminal on the alternator is because, with a DIODE based isolator, there is a voltage drop of approximately 0.8 volts between the center alternator post and the two battery posts.  The batteries will not receive sufficient voltage to achieve full charge.  This problem can be overcome by either using an alternator with a "sense" terminal, OR by using an isolator that does not suffer the voltage drop between the posts.  The Victron ArgoFET meets this requirement.

I want to thank everyone for all of the advice leading up to and since our purchase in November. We spent several months sorting things out, and thanks to Bob, Gary, Keith, and Virginia in Nacogdoches (and nearby), our coach is running great. We had the bulkhead repair completed and a dozen other smaller repairs/replacements. We couldn't be happier with the Grand Villa and so appreciate both the people here and in Texas. Have a great week.