RHEEM EEMAX & ECOSMART Temperature Sensor/Thermistor HA-P134

The RHEEM EEMAX & ECOSMART HA-P134 is an OEM NTC thermistor used in Rheem, Eemax, EcoSmart, Richmond, and related tankless electric water heaters. It measures inlet and/or outlet water temperature so the control board can modulate heating elements, maintain setpoint, and trigger safety or error logic.

Replacing a failed sensor restores accurate temperature feedback. That typically clears E1, E2, or E3 error codes, stops lukewarm or no-hot-water complaints, and brings the unit back to designed performance without guessing at board or element failures. OEM calibration keeps readings consistent with the original control program, which aftermarket sensors of the wrong curve often do not.

Features and benefits

• OEM NTC thermistor matched to the original Rheem/Eemax control boards — correct resistance-vs-temperature curve so the unit heats to the intended temperature instead of overshooting, undershooting, or locking out.
• Direct plug-in replacement for the factory sensors on the listed models — no splicing or adapter in most cases.
• Two common lead-color versions exist in the field: red/yellow (often listed as THRM QC MEDLRG) and older all-red (THRM MEDLRG). Confirm your existing leads before ordering.
• Resolves the most common “no heat / lukewarm / error code” failures caused by an open, shorted, or drifted thermistor.
• Compact sensor body with flying leads designed to seat in the heat-exchanger or manifold pocket used on these tankless units.

Dimensions Exact published envelope dimensions for the HA-P134 assembly are not listed on manufacturer or parts sheets. It is a small probe-style NTC thermistor with insulated leads that terminate in a connector for the control board. Physical size is typical of tankless water-heater temperature sensors (short probe + several inches of lead wire). Compare the new part to the one you remove for lead length and connector style.

Compatibility Fits these families and equivalent kW sizes (including many 8 kW, 11 kW, and 13 kW variants of the same platforms):

• Rheem: RTEX-18, RTEX-24, RTEX-27, RETEX-18, RETEX-24, RETEX-27
• Richmond: RMTEX-18, RMTEX-24, RMTEX-27
• Eemax HomeAdvantage: HA018240, HA024240, HA027240
• Eemax ProAdvantage: PR018240, PRO24240, PR027240
• Eemax: EEM24018, EEM24024, EEM24027 (blue-color units)
• EcoSmart: Eco18, Eco24, Eco27
• iHeat / Drakken: AHS27D, AHS18D, AH27, AH18

Always match the original part number (HA-P134 / RTE10723) and lead colors on the unit you are servicing. Cross-check the water heater model number on the rating plate before purchase.