Benny is supplying 120v to the converter , which puts out "12v" DC. It should be 13.6v. 18.2v will damage the 12v systems, such as the fridge which should not see more than 15.4v.
A 1999 will likely have a Magnetek 6300 converter, which will do over-voltage when its components wear out. Stop until you get that converter turned off and just run the 12v systems on battery. You can use any old 12v battery charger until you can replace the 6300.
There are several choices for replacing the old 6300, but stay away from the Ultra (a WFCO) and the 7300 (which is way better but still single voltage 13.6, no 14.x voltage stage that many batteries need to be properly charged.)
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.