Replaced AGS senor with new, heater fires and runs for three minutes then stops heating and the AGS code is back on. All filters are clean, water flow is good and I have cleaned the heating coils. Anything else I can try?
A bad internal bypass usually causes AGS errors. Too much water bypasses the heat exchanger internally, and the water that comes out is too hot, tripping the AGS switch in the manifold.
Remove the leads from the AGS sensor and connect them together. Temp only for the test.
Then, check the continuity of the sensor. It should be closed.
Start the heater. If the sensor opens, immediately turn off the heater.
If the sensor opens, it might be a bad sensor, or the water is overheating.
To test the sensor, put it in hot water to see where it opens.
The board is bad if the sensor does not open and the heater shuts off with an AGS light.
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