Came out today to diagnose a crown boiler system that was not heating. Upon inspection I found that a thermal cut off switch that is creating an intermittent issue. The thermal cut off switch has signs of arcing. The thermal cut off switch should be replaced to ensure optimal condition. Recommended performing preventative maintenance and homeowner agreed. Performed preventative maintenance, model #Awi1623nlt1psu serial #Piplft000511215. Powered the system down and removed the access panels removed and cleaned burners and cleaned burner box. Checked all electrical connections to ensure that they are secure and in good condition. Thermal cut off will need to be replaced due to intermittent issues. Water pressure is at 15psi and the limit is set for 180°. Powered system back up and called for heat I observed system operate normally and performed combustion analysis test O2 is at 14.1% and CO is at 2ppm. Inspected all copper piping for leaks and corrosion. Tested all 3 zone valves to ensu