1. The buttons on the refer. AUTO button will engage the 120 volt heating section when plugged into shore 120 power. On AUTO, if you disconnect 120 shore power, the refer will auto switch to LP and you will hear that click sound for about 30 seconds. IF NO light of burner, the clicking stops and you will have a CHECK light by those buttons. Make sure the LP is ON and you may have to attempt lighting on LP 7 to 10 times to purge the LP line of air
2. On GAS, when this button is pushed, the refer will ONLY operate on LP gas.
3. Normal operation is on AUTO. Since most of the time you will be on Shore 120 volt power.
4. IF this is the problem and you connect 120 shore Power and the refer attempts to light, you either have NO 12 volt battery on the trailer or that Battery is BAD or you have a battery disconnect. The RV needs a good RV deep cycle battery to operate at its peak efficientcy. Doug