Massey Ferguson 10.02.31 – AIRCON: Issue With Signal To Left Cab Fan Speed Controller (AIRCON)

The system has detected an input error from the fan speed potentiometer or the fan speed controller. The signal is outside of its normal operating range, triggering a "Fan speed controller no. 1 return error". This usually means the blower motor resistor/controller has failed, or there is a short/open circuit in the wiring.

• 7724S
• 5712SL
• 7722
• 7722S
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7726S
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4707
• 4708
• 4709
• 4710
• 5410–5480
• 5608–5613
• 5709S/SL through 5713S/SL
• 6445–6499
• 6612–6616
• 6712S–6718S
• 7465–7499
• 7614–7626
• 7714–7726S
• 8200 Series
• 8400 Series

1. 1

   Inspect the Wiring Harness: Check the wiring and connectors leading to the left cab blower motor resistor/controller (usually located in the cab roof HVAC housing). Look for melted plastic, corrosion, or loose pins, which are common when blower resistors overheat.

2. 2

   Test the Potentiometer: Test the fan speed dial on the climate control panel to ensure it is sending the correct reference voltage to the controller.

3. 3

   Check the Blower Motor: Spin the left blower motor by hand to check for binding, and test its amperage draw. If the motor is failing, it will immediately burn out the new controller.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Access the HVAC Unit

   Open the cab roof hatch or remove the interior headliner panels to access the left-side HVAC blower housing.

3. 3

   Locate the Controller

   Locate the left cab fan speed controller (blower motor resistor), which is typically mounted directly into the blower housing ductwork to allow airflow to cool it.

4. 4

   Remove the Faulty Unit

   Disconnect the electrical pigtail from the controller. Remove the mounting screws and pull the resistor module out of the housing.

5. 5

   Install the New Part

   Insert the new fan speed controller, secure it with the mounting screws, and plug in the electrical connector.

6. 6

   Reassemble and Test

   Reconnect the battery. Turn the ignition on and test the left cab fan through all speed settings. Clear the 10.02.31 fault code using a diagnostic tool or via the tractor's dash menu.