Problem with my Pentair Mastertemp 400 NG heater. It will fire up but only run for a few minutes before shutting down, and Service Heater light comes on. The SFS led is lit. I've replaced the stack flue sensor, the thermostat, and the thermistor. Finally got a pool technician to look at it and he said there's a problem with the heat exchanger. He said they do not service that part due to liability issues, and that I could either clean or replace the heat exchanger on my own or replace the entire heater.
So I'm trying to figure out how difficult it is to replace the tube coil assembly but I can't find any tutorials anywhere. Does anyone know how to do this? I can sling a wrench, but prefer to see a how-to video or guide beforehand.