Case IH A-G-551 - Display – Display: Guidance Speed Mismatch

Discrepancy between the ground speed reported by the guidance system (GNSS/GPS "VT ISO speed") and the physical speed measured by the vehicle's internal sensors (such as the radar, wheel speed sensor, or transmission alternator speed signal).

• MAGNUM AFS Connect
• STEIGER AFS Connect
• Magnum AFS Connect series
• Magnum 400 AFS Connect
• Steiger series
• Optum series

1. 1

   Verify GPS Offsets: Navigate to the 'GPS Setup' screen (Home > Toolbox > GPS) and ensure the GPS 'Forward Offset' value is measured correctly (the physical distance from the GPS receiver to the vehicle reference point).

2. 2

   Compare Speed Sources: Check the 'VT ISO speed' generated by the GNSS system against the tractor's wheel speed or the implement's 'Planter Wheel Speed' to see how far off the values are.

3. 3

   Check Speed Source Priority: Verify the 'Speed Source Priority' settings in the display's Universal Terminal (UT) configurations to ensure the system is looking at the correct primary sensor.

4. 4

   Inspect Physical Sensors: Check the radar and wheel speed sensors for physical damage, debris, or wiring faults, as sensor misreads are a primary cause of speed mismatches.

1. 1

   Correct GPS Configuration

   If the GPS Forward Offset is incorrect, enter the exact physical measurement into the display to align the GNSS calculations with the tractor's pivot point.

2. 2

   Calibrate the Radar / Speed Sensor

   Initiate a speed calibration course using the display's calibration wizard. Drive the measured course at a steady operating speed and press the 'Stop' button. Verify that the 'Radar Measured' window displays a length that matches the actual physical course driven.

3. 3

   Configure Implement Speed

   If pulling an implement like a planter, ensure the speed and wheel speed are present on the ISOBUS. If the GNSS speed drops out, you may need to press the 'Manual Input' radio button to set a fixed manual speed temporarily.

4. 4

   Replace Faulty Sensors

   If the radar or wheel speed sensor consistently misreports data after calibration, or if the wiring harness is shorted/open, replace the defective sensor.