Blue Sea, buy once cry once. Used them on boats in salt water, when I got my RV and had the cheap trombetta go out I replaced with:
https://www.bluesea.com/products/category/35/91/Automatic_Charging_Relays/ML-ACRs.Its bistable with hysteresis so no chatter under any condition, silver plated contacts rated at 300 amp live switching, 500 continuous, 700 for 5 minutes and 1450 for 30 second cranking.
It detects charging voltage on either side and engages in auto mode (so alternator charges house and shore charges starting) or the switch can be set manual on or manual off. Switch has a light letting you know its engaged. Direct replacement using same wires for combine switch that was already there (had to run extra wire for status light)
