Have an SR400 converted to propane. Approx. 15 years old. Just finished replacing the: Tube sheet, igniter, insulation, thermal regulator, new manifold with new sensors and bypass valve, Ignition control module, main circuit board and finally the stack flue sensor. Circuit board is rev. 8 and lights up normally but when I start the heater the fan comes on, the heater fires and begins heating, runs for about 30 seconds-1 minute then stops with the error code 05 and SFS light on back of board. Have checked the exhaust temp with an infrared thermometer, never exceeds 250 f. Everything has been replaced that I can imagine causing a problem. Btw, the propane tank is full.
I have seen other people referencing holding the pool on button down to display flue temperature, but that doesn't work with my heater. It flashes 33 then shows 27. Should it or is that true for newer heaters only? Does that possibly indicate a bad control circuit board? Is there a way to test?
The new Stack Flue Sensor tests normally, ambient temp shows around 3.6 M ohm and the resistance goes down as the sensor is heated. I am not too bright when it comes to electronics so at the risk of sounding stupid I will ask if it should show continuity? Neither the old one or the new one does but they both display the appropriate resistance.
I have not tested the thermal regulator yet because it is brand spanking new but since everything else is also I guess I should?
At my wits end,