Do you believe;
Your house batteries and converter are working properly?
Chassis battery not hooked up and afraid to hook up?
You shorted something and it starting burning?
It seems that just connecting the positives of your chassis and house batteries wouldn't do any harm.
You might want to add some pics so we can better help.
You could install an automotive type fuse inline while your troubleshooting.
1996 Tioga Class C
400 amp/hrs solar, Trimetric
2007 Monaco Diplomat 40 PDQ