Upon arrival spoke to customer. Customer did his own diagnostics prior to our arrival. While on site had customer set thermostat to call for heat. System is on/running. Monitor system for 15-20 minutes no issues or error code present. Shut system down and tested all safety switches. Clean flame sensor flame rod. Inspect and test hot surface igniter. Check heat exchanger for any signs of crack-ok. Could not replicate cause of failure while on site. System is operating normally. Customer is aware that system is showing intermittent issue and could fail at any time. Customer is aware that system is beyond its life expectancy and should consider replacement options based on system age and performance. Customer is looking for the office to provide a quote on replacement options for his 14yr old 50Gal HWH and His 20+yr old furnace. Customer is also looking to add AC coil and condenser to this new furnace installation. Comfort advisor is needed on site. Office to follow up with customer. View