ATC 001549.04 – Heater Valve (Adjusting Motor) Voltage Too Low. John Deere System Advisory.

ATC 001549.04 (ATC 1549.04)

Code: 001549.04

Shortcode: 1549.04


The error code, ATC 001549.04, is triggered when the control unit detects abnormally low voltage at the motor connecting leads (2016 and/or 2027) for the heater valve (B131). This low voltage usually indicates that the circuit is grounded, which can impair the function of the heater valve’s adjusting motor, potentially leading to inadequate heating control within the cabin.


The low voltage condition may result in the heater valve motor failing to operate correctly, which could lead to poor heating performance and discomfort within the vehicle’s interior during cold weather.


  • Inspect Wiring and Connections: Check the wiring and connections at leads 2016 and 2027 for any signs of wear, corrosion, or grounding that might be causing the low voltage issue.
  • Measure Voltage Levels: Use a multimeter to measure the voltage at the motor leads to verify the low voltage condition and help pinpoint the location of the grounding.
  • Identify and Repair Ground Faults: Locate and fix any faults where the circuit may be grounding inappropriately. Replace or repair damaged wiring or components as necessary.
  • Test Heater Valve Motor Functionality: After addressing the electrical issues, test the heater valve motor to ensure it operates correctly and adjusts the valve as required for proper cabin heating.
  • Reset System and Perform Functional Test: Clear any fault codes from the system and conduct a full operational test of the HVAC system to ensure that all components function correctly and that the issue has been fully resolved.


Maintaining the electrical integrity of components within the HVAC system is critical for ensuring consistent and reliable operation. Regular checks and timely repairs of electrical issues are crucial to avoid operational disruptions and maintain cabin comfort. Addressing these electrical faults promptly ensures that the heater valve and other related components function efficiently, thereby enhancing the overall safety and comfort of the vehicle’s occupants.