Upon arrival spoke with customer who’s explaining that boiler was drain yesterday. Customer then noticed that boiler would not fired to provide heat. Automatic water feeder and Automatic low water cut off is operating correctly. Found water level half way @ sight glass. Bypassed thermostat to have boiler fired. While inspecting boiler operation notice water levels are bouncing @ sight glass. Explained to customer about water surging and I’m recommending a chemical treatment to help with boiler surging. Boiler operation was ran and check normally. Had thermostat call for heat once more. Boiler fires up and runs. Cycle boiler a few times for normal operation. Shut boiler down from service switch. When power is applied back to boiler, boiler began to work again normally. Not seeing any issues or problems while on site. Boiler was left operational @ this time. Possible cause of boiler failure. Low water @ boiler. Customer is also looking to have baseboard pump for basement zone relocated i