Pentair Mastertemp 250 - Stack Flue Sensor

[matzb]

About a week ago my heater stopped working and red service light was on. No codes were showing on the display.
I removed the panels looked at the the led on the back side of the control unit and the SFS led was lit. I replaced the SFS sensor and everything worked great until today when the same problem happened. I supposed it is possible for the SFS to go bad in a week, but I suspect something else is causing the problem. If the sensors are failing, why wouldn't I get an E05 Code?

 

[ajw22]

Welcome to TFP.

You only get an E05 error if the SFS is open at startup.

Read Pentair MasterTemp Heaters - Further Reading

 

[1poolman1]

Make sure you have good exhaust flow with nothing blocking the internal blower opening. I have seen spider nests (and rodents) block that opening and cause the issue you see.