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The GP20 "Thermistor is not connected"

The thermistor monitors temperatures inside the GP20 for safety. The “Thermistor is not connected” error can appear on either the Shredder (top machine) or Granulator (bottom machine). This indicates that the cables or thermistor for the affected machine specifically are affected.

Possible Causes

  1. The data cables between the Controlbox (mainboard) and Granulator or Shredder are not properly connected.
  2. The thermistor is not properly connected to the mainboard.
  3. The thermistor itself is damaged.

warnning : Always disconnect power cables before performing any maintenance. Never touch high-voltage components inside the machines.


Note:

  • Step 1 (cable check) is only relevant for errors with Thermistor 3 or 4.
  • Step 2 (mainboard connection) is only relevant for errors with Thermistor 1.
Thermistor Location Notes
Thermistor 1 Inside motor Connected directly to mainboard inside controlbox
Thermistor 2 Not present —
Thermistor 3 Chamber (DB25 connector) Granulator: only thermistor present. Shredder (older versions) at top of chamber
Thermistor 4 Chamber (DB25 connector) Shredder (older versions) at bottom of chamber





Step 1 - Check Data Cables (Thermistor 3 & 4)

warning-iso_V2 Caution

Electrical hazard. If instructed, ensure to disconnect any power cables and ensure to NEVER touch the high voltage power supply seated inside the machine.

  • TURN OFF both machines and DISCONNECT power cables.
  • Inspect the external data cable connecting the Controlbox to the affected Granulator or Shredder.
  • Ensure the cable is fully inserted and free from debris.
  • Optionally, use non-conductive contact cleaner to improve connectivity.
  • Confirm the cable is connected to the correct ports at both ends.
  • Reconnect power and check if the error persists


 Thermistor-cables

Step 2 - Check Mainboard Connection (Thermistor 1)

Note:

If the granulator (bottom machine) is affected, this step requires to disassemble and remove the Shredder unit (mounted on top) before conducting this procedure.


  1. TURN OFF both machines and DISCONNECT both power cables.
  2. Remove the top panel of the machine where is the motherboard; this is the panel containing the red emergency stop.
  3. Unplug and plug back the connector of the thermistor from the mother board, as displayed in the photo.
    1. Optional: Use non-conductive 'contact cleaner' spray to clean the port and improve connectivity.
  4. Reinstall the top panel.
  5. Reconnect both power cables and start the machine to see if the issue is resolved.

Step 3 - Verify Thermistor Function with a Multimeter

If Steps 1 and 2 do not resolve the error, the thermistor or cable may be damaged. You can check the thermistor’s resistance using a multimeter.

Thermistor 1 (Motor)

  1. Unplug the motor thermistor cable from the mainboard.
  2. Measure resistance across the two pins of the connector on the cable.
  3. Expected resistance:
    • Cold: ~100 Ω
    • Room temperature: ~250 Ω
    • Warm: ~500 Ω
  4. If resistance is outside this range, or no connection is detected, the motor must be replaced.

Thermistor 3 & 4 (Chamber)

  1. Unplug the cable between the controlbox and Granulator/Shredder.
  2. On the DB25 connector mounted on the shredder chamber:
    • Thermistor 3 → measure between pins 6 and 8
    • Thermistor 4 → measure between pins 6 and 20
      (Pin numbers are very small—use extra light.)
  3. Expected resistance:
    • Cold: ~50 kΩ
    • Room temperature: ~100 kΩ
    • Warm: ~300 kΩ
  4. If resistance is outside this range, or no connection is detected, the thermistor must be replaced.
  5. If resistance is correct, the cable may be broken. Test continuity between the same pins on both ends of the cable.


    Step 4 – Replace Thermistor

    If the previous steps do not resolve the error:

    • The thermistor, cable, or connector may be damaged and requires replacement.

Contact support

Please contact us for instructions and further help, to have your thermistor replaced.