Get yourself an inexpensive multimeter or test lights to check your main voltages. Main coach batteries should have a range of 12.4 volts to 12.8 volts when the batteries are not being charged. If your readings are below 12 volts, they are too low. Air-conditioning voltage is between 108 volts and 130 volts. If the voltage is higher or lower, this indicates a problem that needs to be repaired.