John Deere 000871.04 – ATC: Air Conditioning Pressure Sensor Voltage Low

The Automatic Temperature Control (ATC) unit has detected an abnormally low voltage signal (below 0 volts) from the air conditioning refrigerant pressure sensor. This indicates that the electrical circuit between the sensor and the controller is either open or shorted to ground. As a protective measure, the controller may restrict temperature control functions and de-energize the A/C compressor clutch to prevent system damage.

• 6020
• 6820
• 6920
• 6920S
• 7715
• 7815
• 7720
• 7820
• 7920
• 8R Series
• 8230T
• 8330T
• 8430T
• 724L
• 9450
• 9550
• 9650
• 6100
• 6200
• 6300
• 6400

1. 1

   Visually inspect the wiring harness leading to the A/C pressure sensor for chafing, breaks, or corrosion, and ensure the connector is secure with clean contacts.

2. 2

   Check the static pressure of the refrigerant system using A/C manifold gauges. A pressure near zero indicates a refrigerant leak that must be repaired before diagnosing electrical faults.

3. 3

   Test the sensor circuit for continuity using a multimeter. With adequate system pressure, a normally closed switch should show low resistance. Infinite resistance indicates a faulty switch or low refrigerant pressure.

4. 4

   Test the wiring circuit between the sensor and the controller for an open circuit or a short to ground.

5. 5

   Inspect the A/C condenser for dirt and debris, and ensure the cab recirculation air filter is clean.

1. 1

   Recover Refrigerant

   The A/C system is under pressure. Before replacing the sensor, the refrigerant must be safely recovered using certified A/C service equipment. Failure to do so can result in personal injury and is environmentally harmful.

2. 2

   Disconnect the Battery

   Disconnect the negative battery terminal to prevent any electrical shorts during the repair.

3. 3

   Locate the Sensor

   The A/C pressure sensor (or switch) is typically located on the high-pressure side of the system. It is often screwed into the receiver-drier (accumulator) or directly into a high-pressure line, frequently near the radiator. On some models, a low-pressure switch can be found under the instructional seat.

4. 4

   Disconnect Electrical Connector

   Carefully detach the electrical connector from the old sensor.

5. 5

   Remove the Old Sensor

   Using the appropriate size wrench, unscrew the old pressure sensor from its fitting. Be prepared for a small amount of residual oil to escape.

6. 6

   Install the New Sensor

   Ensure the O-ring on the new sensor is lubricated with refrigerant oil. Screw the new sensor into place and tighten it to the manufacturer's specified torque. Do not overtighten.

7. 7

   Reconnect Electrical Connector

   Securely attach the electrical connector to the new sensor.

8. 8

   Evacuate and Recharge the System

   Use A/C service equipment to pull a vacuum on the system to remove any air and moisture. Then, recharge the system with the correct type and amount of refrigerant as specified by John Deere for the particular machine.

9. 9

   Reconnect Battery and Test

   Reconnect the battery. Start the machine and turn on the A/C system. Check for proper operation and ensure the fault code does not return.