Re: 1992 Dodge house battery not charging while vehicle running
Dave is right on with the Isolator, which is what the '92's had. Probably a Surepower model 1302. Very common for these to have corrosion at the terminals, or loose terminals also. You'll want to seriously consider going to a Battery Separator if the Isolator is bad, you may want to update to the Separator anyway.
I just re-read your post and noticed that it was the house battery that wasn't charging, you probably have a bad 50 amp auto-reset circuit breaker.To locate the circuit breaker, you'll want to first find the Isolator (about 3"x3"x7" with fins). Trace the large wire from the Alternator, it will connect to the center terminal on the Isolator. The outer terminals are for the house and starting batterys. Trace the wires on these outer terminals, one will go to a factory Dodge power distribution box, the other will connect to a small metal cased 50 amp Auto-reset circuit breaker, and then continue on to the house battery. This 50 amp Auto-reset circuit breaker would corrode internally and cause all types of problems. On later model SMB's with the Isolator (pre-Battery Separator models), the 50 amp circuit breaker was omitted from the system. You can either replace the circuit breaker, or bypass and omit it like the later models.
If you omit the circuit breaker, make sure you trace the wire all the way to the house battery to confirm it is not subject to any chaffing or shorting out. Add cable/wire loom as needed if you are concerned about any potential wear areas.