Master temp 175 AGS error

What I have already done is made sure the water flow was already good with no blockages. Something to note is that I cannot adjust the temperature or turn off or on the heater at the display. The heater fires up for about 30 seconds to two minutes, and then turns off.
 
Something to note is that I cannot adjust the temperature or turn off or on the heater at the display.

Replace the membrane keypad.

Check the thermal regulator opens at 120F under hot water,

Check the internal bypass valve.


Check the stack flue temperature.

While running, press and hold the On button to display the exhaust temperature once you replace the membrane keypad.

Here is what the normal exhaust temperature should be:

  • Below 250 degrees...very low
  • 250 to 290 ..................low
  • 290 to 350.................acceptable
  • 350 to 480 ..................high
  • Above 480...................error/shutdown.
Note: HD models can be up to 75 degrees higher. HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.

If the exhaust gas temperature is higher then normal then water may be bypassing the heat exchanger through a broken bypass valve.
 
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