So this heater started having issues this summer. I turn the pool button on,cycles 3 times trying to light then turns off. Says service heater with no lights on the back indicating any issues. I have replace flu stack, thermistor twice, the high limit switch, ceramic igniter twice, the Fenwal ignition control. Still doesn’t work. If I cover the intake air flow about half way it will heat for about 3 seconds then turn off. Any advice would be great. I have a couple hundred into replacement parts and want it to work a couple more years as the copper in the bucket are in good shape still.