u/Chemical_Ad1196

Opened my pool this year and my heater started showing an E01 error. I replaced the thermistor and it worked one more time and then stared showing the E01 again. I replaced the main board and I’m still seeing the dreaded E01 error. Any suggestions on where to troubleshoot next. All fires and tubes look good. When I try to power it on, I sometimes hear the fan try to start followed by a click and the E01. Most of the time I power on it clicks immediately with the E01.

Heater is about 5 years old.