John Deere 524219.02 – ATC (Automatic Temperature Control Unit): B143 Defog Sensor, Frequency Out of Valid Range

Triggered when the control unit detects that the frequency signal coming from the windshield defog sensor (B143, lead 2003) is outside the valid operational frequency range of 32.26 – 37.88 Hz, indicating a malfunction within the sensor itself or its associated circuitry.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6230
• 6330
• 6430
• 6120
• 6220
• 6320
• 6420
• 6820
• 6920
• 6920S

1. 1

   Visually inspect the B143 defog sensor and its wiring harness (specifically lead 2003) for signs of physical damage, corrosion, or loose connections.

2. 2

   Measure the frequency output of the defog sensor at the signal input using a multimeter or diagnostic tool to verify if it falls within the valid range of 32.26 – 37.88 Hz.

3. 3

   Ensure the circuit is not shorted to a supply lead or ground.

1. 1

   Repair Circuitry

   If the diagnostic checks reveal damaged wires, corroded pins, or loose connectors on lead 2003, repair or replace the affected wiring harness sections.

2. 2

   Replace the Sensor

   If the wiring is intact but the sensor consistently produces frequencies outside the 32.26 – 37.88 Hz range, the B143 defog sensor has failed internally and must be replaced. Remove the sensor shield and unclip/unscrew the sensor from the windshield mount, disconnect the harness, and install the new sensor.

3. 3

   Test System Functionality

   After repairs or replacement, turn on the system and test the defogger to ensure it activates correctly based on the new sensor's readings.

4. 4

   Clear Codes

   Reset/clear the stored ATC 524219.02 fault code from the system and perform a complete functional check to ensure no further issues are present.