Plugged in but only partial electricity
It sounds like the power converter (Univolt) is either unplugged, a circuit breaker is tripped (the circuit that the Univolt is on), or the power converter (Univolt) has ceased to operate. From your description, it sounds like your water pump, etc. are trying to operate on the limited voltage available from your weakened battery.
The lights and water pump are both strictly 12-vot DC. Your refrigerator and electrical outlets utilize 120-volt AC (unless your refrigerator happens to be a 3-way replacement) -- these will work when plugged into shorepower even if the power converter (Univolt) is not operational and the battery is low or not in place.
Kevin D. Allen
WBCCI (Lifetime Member)/VAC/Free Wheelers #6359
1964 Overlander International/1999 GMC K2500 Suburban (7400 VORTEC/4.11 Differentials)
1978 Argosy Minuet 6.0 Metre/1975 Cadillac Eldorado Convertible (8.2 Liter V8/2.70 Final Drive)