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ERROR CODE 311: OUTPUT THERMISTOR
1) Check that the wire connections are secure and free of
burns or cuts. The output thermistor is located on the
heat exchanger on the right side.
2) Check the resistance value; it should be about 9.0kΩ at
room temperature (about 74°F).
3) Clean the thermistor.
a. Drain the unit of water. See p. 22.
b. Remove the fastener holding the output
thermistor and pull out the sensor probe. Clean
the probe to a silver finish. Do not lose the rubber
o‐ring that wraps around this sensor.
c. Replace and test.
4) If the error code persists, replace the thermistor.
ERROR CODE 321: INLET THERMISTOR
1) Check that the wire connections are secure and free of burns or cuts. The inlet thermistor is
embedded in the water inlet connection.
2) Check the resistance value; it should be about 9.0kΩ at room temperature (about 74°F).
3) Clean the thermistor.
a. Drain the unit of water. See p. 22.
b. Remove the computer board to access the inlet thermistor. The computer is fixed in place by a
single screw at the top of the board.
c. Remove the screw, pull out the sensor probe. Clean the probe to a silver finish. Do not lose the
rubber o‐ring that wraps around this sensor.
d. Replace and test.
4) If the error code persists, replace the thermistor.
Mixing Thermistor
Figure 9
ERROR CODE 331: MIXING THERMISTOR
1) Check that the wire connections are secure and free of burns or cuts. The mixing thermistor is
embedded in the water outlet connection.
2) Check the resistance value; it should be about 9.0kΩ at room temperature (about 74°F).
3) Clean the thermistor.
a. Drain the unit of water. See p. 22.
b. Remove the computer board to access the mixing thermistor. The computer is fixed in place by
a single screw at the top of the board.
c. Remove the screw, pull out the sensor probe. Clean the probe to a silver finish. Do not lose the
red rubber o‐ring that wraps around this sensor.
d. Replace and test.
4) If the error code persists, replace the thermistor.
Inlet Thermistor
Figure 8
Mixing Thermistor
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Troubleshooting Guide
Output Thermistors
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