CLAAS 7620h – Transmission Control Module: High-Pressure Brakes Below 70 Bar

When the tractor is started (initialisation phase), the system expects the high-pressure braking circuit to reach a minimum standby pressure (typically between 77 and 92.9 bar in the accumulators). This code triggers if the pressure in the high-pressure brake circuit fails to reach 70 bar. This condition will trigger an audio warning and cause the brake indicator light to remain steadily "on".

• Arion 410
• Arion 420
• Arion 430
• Arion 510
• Arion 520
• Arion 530
• Arion 540
• Arion 610
• Arion 620
• Arion 630
• Arion 640
• Arion 660

1. 1

   Check the hydraulic fluid level to ensure it is correct, as low fluid can lead to pressure issues

2. 2

   Perform a visual inspection of the hydraulic brake circuit for any visible signs of leaks, damage to hydraulic lines, or loose connections

3. 3

   Inspect electrical connections and wiring harnesses for the brake pressure sensor and the high-pressure braking solenoid valve for corrosion, damage, or loose connections

4. 4

   Test the functionality of the left-hand (Z126) and right-hand (Z127) brake pedal switches

5. 5

   Monitor brake pressure using the tractor's onboard diagnostics or the CLAAS Diagnostic System (CDS) to see if pressure is consistently low or fails to build

1. 1

   Verify sensor accuracy

   Compare the pressure reading from the sensor in the diagnostic system with a reading from a manual pressure gauge connected to the circuit. If the readings differ significantly, the pressure sensor is likely faulty and must be replaced.

2. 2

   Test solenoid valve

   Check for proper power supply to the high-pressure braking solenoid valve (Y329). Ensure the valve is opening correctly when commanded. A malfunctioning solenoid that is stuck closed or not opening fully will prevent the system from charging.

3. 3

   Inspect brake accumulator

   Check the service brake pressure accumulator. A faulty accumulator with a ruptured diaphragm or incorrect nitrogen pre-charge will fail to hold pressure and requires replacement.

4. 4

   Check for internal leaks

   If no external leaks are found and the sensor/solenoid are functioning, inspect for an internal leak within a component such as a valve block or the brake master cylinder.

5. 5

   Replace faulty components

   Based on the diagnostic findings, replace the faulty component (most likely the brake pressure sensor or the high-pressure braking solenoid valve).

6. 6

   Calibrate system

   After replacing any components in the braking circuit, perform a service brake calibration to ensure proper system operation.