My system was installed at the time of manufacture, and I picked up my motorome at the factory 9 years ago.
The chassis battery consists of two large 12 volt batteries, and the house battery is four 6 volt golf cart batteries.
The alternator is a 160 amp Prestolite Leece Neville.
The Isolator is:
Bi-Directional Isolator Relay Delay Diesel 00-00366-00.
It triggers a solenoid:
White-Rogers/RBM
St Louis MO
Type 586-105111-3 Coil 12 VDC Cont.
Customer # 586-902
It has been working perfectly all these years. The ONLY problem I've ever had with the entire electrical system is recently, the alternator failed to charge after the motorhome was parked for 2 months while I did major repair/mod work on the roof. The problem was one failed slip-ring brush, which now I believe might've been caused by ME.
I only post this because if this solenoid (which is mounted sideways) were to fail, I would replace it with the same one.