Fendt 10.1.3D – A053 - Air Conditioning Control ECU / A038 - Central Electrical System ECU: Water valve stepper motor (heater valve) is not working

The water valve stepper motor (heater valve) is not working or its function is non-operable. The stepper motor is responsible for regulating the flow of hot coolant into the cab's heat exchanger to control the climate temperature.

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• Fendt 300 Vario series
• Fendt 400 Vario series
• Fendt 700 Vario series
• Fendt 800 Vario series
• Fendt 900 Vario series (e.g., 919, 922, 924, 927, 930, 933, 936)

1. 1

   Inspect the wiring harness connecting the A053/A038 ECU to the heater valve stepper motor for breaks, corrosion, or loose pins.

2. 2

   Using a 160-pin adapter box connected to the A038 Central Electrical System ECU, measure the voltage and resistance to the heater valve stepper motor to ensure it is receiving power and signal.

3. 3

   Attempt calibration: Often, the stepper motor simply loses its position limits and needs to be recalibrated via the tractor's terminal.

1. 1

   Turn on the ignition and access the heater/climate control menu on the terminal.

2. 2

   Press the button repeatedly until the heater symbol flashes to initiate the calibration.

3. 3

   Allow the automatic calibration process to run, which takes approximately 30 seconds.

   During this time, the heater valve stepper motor is opened and closed slowly, and the display will flash.

4. 4

   Observe the terminal display for the calibration result.

   If successful, 'O.K.' will appear. If 'ERROR' appears, the stepper motor is physically jammed, burned out, or has a wiring fault and must be replaced.

5. 5

   Turn the ignition key to the '0' (OFF) position and wait for at least 15 seconds before switching the ignition back on.

   This is a crucial step to ensure the ECU saves the parameters.