John Deere 1547.03 – ATC / ETC / ARC: Evaporator Core Temperature Sensor Voltage Too High

The control unit measures a voltage exceeding 5 volts at the signal input for the evaporator core temperature sensor (B129, lead 2018), indicating that the sensor circuit is either open or shorted to a power supply lead. This prevents the HVAC system from accurately reading the evaporator core temperature, leading to improper climate control operation such as overcooling (freezing up) or insufficient cooling.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6M series
• 6R series
• 6020 series
• 6030 series
• 6230
• 6330
• 6430
• 7020 series
• 7720
• 7820
• 7920
• 8020 series
• 8030 series
• 8230T
• 8330T
• 8430T
• 9000 series (R, RT, and RX models)
• 7180
• 7280
• 7380
• 7480
• 7580
• 7780
• 7980
• R4030
• R4038
• R4044
• R4045
• R4060
• 640L
• 648L
• 748L
• E360
• E360LC

1. 1

   Restart the engine to verify if the active Service Code reappears, ruling out a temporary communication glitch.

2. 2

   Visually inspect the wiring harness and connectors at the evaporator core temperature sensor (B129) and lead 2018 for chafing, damage, wear, or loose/corroded pins.

3. 3

   Use a multimeter to back-probe and verify the voltage at the sensor's signal input. A continuous reading of 5V or higher confirms the electrical fault is currently active.

4. 4

   Disconnect the sensor and measure its resistance across its terminals. Compare the reading to the OEM specification for the ambient temperature. If the sensor reads completely open (infinite resistance), it has failed internally.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery ground to prevent electrical spikes during repair.

2. 2

   Repair Harness

   If the diagnostic checks revealed a broken wire or a short to a power lead in the harness, splice and repair the damaged section using OEM-approved weather-sealed connectors, or replace the damaged connector pigtail.

3. 3

   Replace the Sensor

   If the wiring is intact but the sensor failed the resistance test, locate the evaporator core temperature sensor (typically inserted directly into the fins of the HVAC evaporator core inside the cab roof or dash assembly). Carefully pull the old probe out of the evaporator fins and disconnect it. Plug in the new sensor and press the probe securely into the designated location in the evaporator core.

4. 4

   Reassemble and Clear Codes

   Reconnect the battery, turn the key on, and use the CommandCenter display or a diagnostic tool to clear the stored ATC/ETC 001547.03 fault code.

5. 5

   Verify Operation

   Run the machine and turn the A/C on. Verify that the HVAC system operates correctly without freezing up the evaporator and that the code does not return.