Tech returned to replace contactor, 4 burners and ignition control board. Tech found that the 4 original burners are shorter than the truck stock burners. We will need to order four Nutone burners, part number 5186620. Tech cleaned existing burners and flame rod. Replaced ignition board and contactor. Turned power back on and gas pack did not light. Sequence of operations is working correctly, but tech found propane tank missing from the left side of house. Tech left breaker off so ignition control will not lock out. Once customer has propane tank installed and hooked up, unit should heat. Gas and breaker are off to unit. We will need to return to install new burners. Customer will need to call gas company to install and hook up gas tank. Tech collected for all three repairs. Need to return to install prepaid burners.