Description: Thermistors w/ O-ring

Model #: THRM SMLCompatible With: models 8kW, 11kW, & 13kW

Shipping Details: ** Any parts sold after 3pm EST M-F may be shipped next day

 ≈ Ecosmart Eco8, Eco11 ≈ iHeat/Drakken AHS11D, AHS8D
≈ Eemax HomeAdvantage HA013240, HA008240
≈ Eemax ProAdvantage PR008240, PR013240, 
≈ Eemax EEM24008, EEM24013, 
≈ Rheem RTEX-8, RTEX-13
≈ Rheem RETEX-8, RETEX-13
≈ Richmond RMTEX-08, RMTEX-13

A thermistor is a type of resistor whose resistance varies significantly with temperature changes. It is primarily used for temperature sensing or temperature control applications. When a thermistor fails, it may trigger an error code such as E1, E2, E3, or E4 on the control board, or it may result in a complete absence of hot water.

The loss of hot water occurs because the faulty thermistor fails to send accurate temperature readings of the incoming hot and cold water to the control board. Without these critical signals, the control system cannot determine the appropriate response, thus preventing any heating elements from activating as it cannot accurately assess the water temperatures.

To resolve this issue, replacing the faulty thermistor is recommended. This straightforward solution reinstates the unit's ability to accurately monitor and respond to water temperature changes, thereby restoring normal operation.

Testing thermistors is a straightforward process. Follow these steps to diagnose a potential malfunction:

  1. Identify and Disconnect the Thermistors: Locate the red and yellow plugs connected to the control board. These should be positioned directly behind the LED display. Ensure you disconnect these specific plugs and not the similarly colored ones located above, which are smaller.

  2. Run a Diagnostic Test: After disconnecting the thermistors, turn on the hot water and allow it to run for approximately 5 minutes. If hot water is produced during this period, it indicates a malfunctioning thermistor that requires replacement.

  3. Error Code Response: Upon disconnecting the thermistors, if an E1 to E4 error code appears, this is expected. To proceed, press and hold the silver knob for approximately 3 seconds and then release it. This should display a CE error code, allowing you to continue testing the hot water functionality.

  4. Control Board Considerations: Note that depending on the series of the control board, it may not permit bypassing this test. In such cases, it is necessary to replace the thermistor to confirm the diagnosis.

By following these steps, you can effectively assess whether a thermistor replacement is required to restore the proper functioning of your system.