Soft Serve: Replacing Temperature Probe

SS: Replacing Temperature Probe

How-To Guide :Soft Serve :: Replacing Temperature Probe

Spaceman soft serve machines with digital controls use a digital PT100 temperature probe to measure the temperature of the product in both the hopper and the cylinder.  The probe for the hopper and cylinder are the same part number and replacing them is very similar.  The instructions below explain how to replace the temperature probe correctly on all machines.

Special Note: The replacement Temperature Probe can be purchased via PartsTown.  The part number is: This article only applies to Soft Serve machines with digital controls.


Required Tools

  1. Metric Hex Driver or Allen Key Set
  2. Flathead screwdriver set
  3. Philips-head screwdriver set
  4. Side-Cutters or Wire Cutters
  5. Thermal Paste (recommended)
  6. Small Zip Ties and Adhesive Mounts (recommended)
  7. Small Wire Ferrule Crimps (recommended, only required for V1 boards)

How to replace the Hopper Temperature Probe
  1. Power off and unplug the machine.
    Warning: It is very important to unplug the machine.  Power will be active on parts of the machine anytime the machine is plugged in.  Risk of shock.
  2. Version 1, Flat Front Models: Remove Front Cover (if Version 2, skip to Step 3)
    1. Remove the draw switch cover from the front panel by pulling gently while pinching both sides of the cover. 
    2. Remove the two black bolt covers on either side of the front panel
    3. Using a 6mm Allen/Hex key, remove the bolt and washer from both sides of the front panel
    4. From the bottom of the cover, gently pull down and outward to remove the panel.  If the model has metal draw paddles, the panel should gently slide between the paddles and the draw valves.  In some cases, it may be easiest to remove the dispensing door assembly.
      Information: There is generally sufficient excess wiring to be able to hold the panel several inches out from the front of the machine allowing for any repair.  Be careful not to hang or otherwise put excessive force on these wires.  The front panel should be held manually or secured in place by other means during repair.
  3. Version 2, C-Line Models: Remove Front Cover
    1. Using a Philips Head screwdriver, remove the bolts from the bottom of the over-head panel, and set aside.
    2. Gently pull down and out on the panel to remove the front panel from the machine.  
  4. On the side of the machine where the temperature probe is being replaced, using a flathead screwdriver, unlock all panel locks remove the rear and side panels from the machine.  All panel locks are quarter-turn and should turn inward to unlock, they do NOT require significant force to unlock. For floor-standing machines, generally only the top panels need to be removed. 
    Note: For smaller countertop machines, panels may be installed using an 8mm Hex-head bolt rather than quarter-turn panel locks.
  5. Using wire cutters cut the plastic zip ties holding the temperature probe being replaced.  Hopper temperature probes enter through the side of the hopper through a black or white cap, and Cylinder temperature probes can enter through the side, top, or bottom front of the cylinder assembly.   These caps may be covered in an adhesive backed foam for extra protection.  Starting in mid 2021, cylinder temperature probes can now be accessed from behind the front panel for easier replacement
    Note: It is sometimes easiest to also remove the bottom front panel of the machine to replace cylinder temperature probes, especially on older models.
    For 2021 models, only the top front panel has to be removed for cylinder temperature probe replacement

  6. On the control board, loosen the temperature probe connector and disconnect the temperature probe from the board.  For V1 control boards, this will require a small flat head screwdriver, and on V2 control boards, this is a push-to-release connector.
    Important: Pay close attention to how the probe is wired.  One pin on the connector will have two wires twisted together going to it, and the other pin will have only a single wire going to it.  This is more important than the wire color.  We recommend taking a picture of the connector prior to disconnecting.
  7. Pull the temperature probe through the machine away from the control board, notating how the sensor is run.  Do not remove the probe from the Hopper or Cylinder yet.
  8. Carefully remove the adhesive backed foam and probe cap where the temperature sensor goes into the Hopper or Cylinder.  If able, you can salvage the adhesive backed foam, or replace with new foam if available.  
  9. Carefully pull temperature probe from hopper or cylinder.  Use a rag or disposable towel to wipe probe clean of thermal grease.  Remove the cap from the old temperature probe and set aside.  Discard the bad probe.
    Important:  If you do not have extra thermal grease on-hand, be sure to salvage as much thermal paste as possible to reuse on new temperature probe.  We highly recommend adding new grease to the new temperature probe if able.
  10. Remove the new temperature probe from the packaging and slide the cap onto the new temperature probe.
  11. Add thermal grease to the sensor head on the new temperature probe.
  12. Install the new temperature probe into the hopper or cylinder.  Be careful not to damage or crease the new probe.  The probe should be inserted approximately 6-8 inches, and should not require any force.  Insert the probe until you feel the end of the tube inside the hopper or cylinder.
  13. Install the cap and cover with adhesive backed foam.
  14. Route the temperature probe through the machine and to the control board, following the same path the old temperature probe followed.
  15. Twist the two bare wires of like-color together.  This should give you two connections (one white, and one red) to install onto the control board.  Reinstall the probe to the correct pins on the connector as noted during step 6.  The twisted wires should go to the same pin as the twisted wires noted in Step 6.  For V1 boards, it is recommended to use a wire ferrule crimp rather than leaving the wires bare.  For V2 boards, no ferrule crimp is required for the push-to-connect connectors.
  16. Before re-securing the probe, plug in and power on the machine.  Turn the power to on, and press the P button to display the temperatures.  Verify that the temperature displayed is nominal (i.e. not 100+ degrees or some other erroneous value.  At this stage, the temperature should read +/-20 degrees of the actual temperature it is measuring.) 
    Note:  If the temperature reading is still bad, verify all connections are secure, and that the probe is properly inserted into the hopper or cylinder.  In very rare circumstances, if the wiring is all verified as correct, it is possible the control board sensor is bad and the control board needs to be replaced.
  17. If the temperature is within range, turn off power to the machine and unplug from the wall.
  18. Secure the new temperature probe to the inside of the machine using zip ties and zip tie mounts.  Ensure no part of the temperature probe is creased or able to come into contact with any moving parts.
  19. Reinstall the side panels and front panels, reversing steps 1-4.
  20. Follow the steps in the Soft Serve Temperature Calibration article to properly calibrate the new temperature probe.

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