There are 2 reverse polarity fuses in the converter for the battery. There is an inline resettable fuse within 6' of the battery. The battery disconnect switch must be "IN-use".
Stop replacing parts. Buy a multimeter and learn how to use it. YouTube is your friend.
You can not fix electricity without a multimeter.
2011 Keystone Sprinter 323BHS. Retired Master Electrician. Retired Building Inspector.
All Motor Homes are RV's. All RV's are not Motor Homes.