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Product title:

Harman Black Thermistor Exhaust Sensing Probe (ESP): 3-20-11744

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Product SKU ! 3-20-11744
Product MPN ! 3-20-11744
Product availability: In Stock
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Replacement Harman Black Exhaust Sensing Probe (ESP) for select pellet stoves.

A 3 blink error code means that the control board has not detected the ESP (Exhaust Sensing Probe) at startup or that it lost communication with it while the unit was running.

  • Verify that the ESP probe is clean by removing it and looking at it, clean if necessary. It should be a silver-colored metal.
  • If you replace it, make sure you replace it with the proper one for your unit. There are two versions; a probe with black wires and a probe with red wires, replace accordingly.
  • If the probe itself looks “bent” it’s probably broken.
  • Before replacing the probe verify that the probe itself is actually plugged into the controller and the contacts on the controller are “clean”
  • On the front side of each controller, there is a red rectangle box with a series of 8 micro-switches called DIP switches. The controller must be removed from the unit to access them. DIP switches allow multiple stoves to use the same controller but run different programs according to the stove’s required functions. The #5 DIP switch must be set to “OFF’ or down for ESP probes with black wires and set to “ON” for DIP switches with red wires. 3 blink error codes can be caused by installing the improper colored wired ESP with the wrong DIP selection.

Also compatible With Eco Choice BA100

    Fitment Note: There are multiple colors of ESP probes for Harman stoves. If your stove has a Black, White, or Yellow probe, this black probe is the correct replacement. If you have a Red ESP Probe, you require part 3-20-00844

    Replacement For Part Numbers:

    • 3-20-11744
    • 1-00-00744

    View Compatible Models

    UPC: 652174647279

    Compatible Models


    • Accentra Cast FS
    • Accentra Insert (Pre: 008241201)
    • Advance (Pre: 008360001)
    • DVC 500 (Pre: 008065076)
    • Invincible Insert
    • Invincible RS
    • Magnum (44 Mag)
    • P38
    • P38+ (Pre: 008190059)
    • P61-A (Pre: 008085055)
    • P61A (Pre: 008085803)
    • P68 (Pre: 008281295)
    • PB105
    • PC45 (Pre: 008055031)
    • PF100
    • XXV (Pre: 008200828)

    Technical Specs

    Probe Length 2 1/2"
    Wire Length 60"



    Install Instructions For Harman Black Thermistor Exhaust Sensing Probe (ESP): 3-20-11744

    You must be careful not to bend an ESP probe if removing it for maintenance purposes. Bending the sheath of the probe will usually ruin the sensor. Likewise, when cleaning your stove, care should be taken to not bend the sensor when cleaning. Do not send brushes or vacuum tools through the stove blindly. Before cleaning your stove for the first time, find the ESP probe and make sure that it is not going to be in the way when cleaning. If it is, remove it from its mount prior to performing work.

    Using a 1/4" socket, remove the mounting screw and remove the thermocouple from the stove. Trace the wires back to the control board and unplug the wires.

    DIP Setting by Stove Model


    The Control Board/ESP combination is responsible for all high limit safety control. There are 2 high limits, one normal operation high limit and one backup high limit. The control has an automatic diagnostic circuit that continuously monitors the ESP and Room Sensor for faults. If a fault should occur, the control sends a status alert and at the same time the unit goes down to minimum feed/ minimum burn as a safety condition.

    In 2008 Harman changed the ESP probe for all units going forward. The change is notable by the color of the ESP wires, Black wires are Pre 2008 and Red Wires are Post 2008. THESE WERE ROLLING CHANGES AS NEW UNITS WERE MADE AND NOT ALL CHANGES HAPPENED JAN 1 2008.

    • For most units, dependent on the controller and/ revision, red thermocouples can be use in place of black thermocouples if the #5 DIP switch settings on the control board are set to 'ON', or 'UP'.

    • Black thermocouples have the #5 DIP switch setting 'OFF', or 'DOWN' however; red thermocouples are slightly larger in diameter than black ones and often will not fit into the mounting holes of black thermocouples on some units.

    • RED ESP wires cannot be cut and spliced.

    • Circuit board revisions ultimately dictate whether a black or red ESP should be used. See the chart below...