Max-E-400 heater


New member
Jul 29, 2019
Heater starts OK, after a few sec. when gas burner starts I hear noise like whining and heater
stops with E05 error and STS light on the PC board. Replaced air blower switch and the same.
Should I replace blower or just blower motor?
It was running fine this year.


TFP Expert
Mar 2, 2011
Usually overheating or an open stack flue sensor.

On startup, press the pool on button until the stack flue temperature is displayed and report what it goes to.

The following are the LEDs:

1.....PS (Pressure Switch)
2.....HLS (High Limit Switch)
3.....SFS (Stack Flue Sensor)
4.....AFS (Air Flow Switch)
5.....AGS (Automatic Gas Shutoff).
6.....Service System
9.....Pool On
10...Spa On
11...Service Heater.

Since the error light was SFS, that's the stack flue sensor.

AFS would be an air flow issue.
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