I am assuming your '85 does not have a battery cut-off switch on the frame just behind the battery. This means your battery is always available (when charged) to power your 12 volt equipment ( heat, fridge when on propane, lights, water pump, radio, hot water heater when on propane, propane leak detector). You will not have any of your 120 volt electric outlets available or your microwave, or air conditioning. Plugging your camper into shore power should automatically activate these 120 volt items as well as recharge your battery using the on-board converter. The converter is the box with the fuses and circuit breakers in it. Fuses for 12 volt side, breakers for 120 volt side. If there is a breaker for the hot water heater, always keep it off until you fill the hot water tank. To go from 12 volt (battery) power to full 12 volt plus 120 volt capacity, just plug your camper into am appropriate power source (usually a 30 amp circuit) using your camper power cord. If you plug in to a regular home outlet (15/20 amp) using an adapter, make sure use a 12 short 12 gauge extension cord. I also do not recommend running air conditioning in this situation. Another note, check inside your fridge for a small climate control switch. If you have one, make sure it is off when using battery power. It will draw down the battery in a very short time.