CLAAS 751Fh – MFA (A100): Hexactiv Signal Voltage Incoherent

The fault code indicates an incoherent voltage signal from the Hexactiv automation contact (S192) processed by the MFA (A100) armrest multifunction module. The signal is illogical or does not correspond to an expected state (e.g., neither definitively on nor off, or erratic). This fault results in the immediate deactivation of the Hexactiv function, which is responsible for automatic gear shifting based on engine load and speed.

• Axion 810
• Axion 820
• Axion 830
• Axion 840
• Axion 850

1. 1

   Confirm that fault code 751Fh is active in the MFA (A100) module using a CLAAS diagnostic tool and note any other active fault codes.

2. 2

   Visually inspect the wiring harness and connectors associated with the multifunction armrest and the Hexactiv switch for any visible damage, corrosion, or loose connections.

3. 3

   Check the Hexactiv Switch (S192) for correct mechanical operation.

4. 4

   Test the continuity of the Hexactiv Switch (S192) in both its on and off states.

5. 5

   Check for short circuits to power or ground in the Hexactiv switch wiring.

6. 6

   If the switch and wiring are found to be in good order, evaluate the MFA (A100) module as the potential cause.

1. 1

   Isolate the issue

   Based on the diagnostic checks, determine if the fault lies with the Hexactiv automation contact (S192), the wiring, or the MFA (A100) module.

2. 2

   Repair wiring and connectors

   If any damaged wiring or corroded connectors are found, repair or replace them as necessary. Ensure all connections are clean and secure. Apply dielectric grease to connectors to help prevent future moisture ingress.

3. 3

   Replace Hexactiv switch (S192)

   If the switch is determined to be faulty, access it on the multifunction armrest. Disconnect the electrical connector, remove the old switch from its mounting, install the new switch securely, and reconnect the electrical connector.

4. 4

   Replace MFA (A100) module

   If the switch and wiring are confirmed to be good, the MFA (A100) module may be the cause and should be replaced. Note that this is a more complex task and may require programming with the CLAAS Diagnostic System (CDS).

5. 5

   Clear fault codes and test

   After completing the repairs, clear all fault codes using a diagnostic tool. Operate the tractor and engage the Hexactiv function to confirm that the fault has been resolved.