John Deere 1547.04 – ATC: Evaporator Core Temperature Sensor Voltage Too Low

The control unit measures below 0 volts at the signal input of the evaporator core temperature sending unit (sensor B129, lead 2018), indicating a short to ground in the sensor circuit. As a result, the HVAC system cannot accurately determine the temperature of the evaporator core, and temperature control is restricted to prevent ice formation.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6120-6420
• 6120L-6520L
• 6M series
• 6R series
• 7715
• 7815
• 7720
• 7820
• 7920
• 7R series
• 8120-8520
• 8230T
• 8330T
• 8430T
• 8R/8RT series
• 9R series
• 9RT series
• 9RX series
• R4030
• R4038
• R4044
• R4045
• R4060
• 640L
• 748L
• 948L
• Wheel Feller Bunchers

1. 1

   Inspect the wiring harness at lead 2018 (connecting the ATC module to sensor B129) for signs of chafing, pinched wires, or exposed copper that could create a short to ground.

2. 2

   Disconnect the sensor and inspect the connector pins for corrosion, moisture ingress, or damage.

3. 3

   Test the resistance of the evaporator core temperature sensor (B129) using a multimeter to check for an internal short.

4. 4

   With the sensor disconnected and the key ON, test the signal wire from the ATC controller for the proper reference voltage (typically 5V). If the voltage is 0V, the short to ground is in the wiring harness.

1. 1

   Power Down

   Turn off the engine and disconnect the battery to ensure safety while working on electrical and HVAC components.

2. 2

   Access the Evaporator Core

   Remove the necessary cab panels/roof cap to access the HVAC unit and the evaporator core area.

3. 3

   Locate Sensor B129

   Find the evaporator core temperature sensor. It is typically a pin-shaped thermistor pressed directly into the evaporator fins.

4. 4

   Repair Wiring (If Applicable)

   If your diagnostic checks revealed a short to ground in lead 2018, repair the damaged section of the wiring harness and secure it away from sharp metal edges.

5. 5

   Replace the Sensor (If Faulty)

   If the sensor is internally shorted, pull the old sensor out of the evaporator fins. Carefully press the new pin-shaped sensor through the evaporator fins, ensuring it is securely positioned to provide stable temperature readings and prevent ice formation.

6. 6

   Reassemble

   Reconnect the sensor wiring harness, reinstall all cab panels, and reconnect the battery.

7. 7

   Clear Codes

   Start the tractor. Use the CommandCenter display or John Deere Service Advisor to acknowledge and clear the ATC 001547.04 service code. Verify that the A/C compressor engages and the system cools properly.