Fendt 04.1.79 – A050 - ECU, basic control unit: Output for the reverse warning signal is not OK

The system has detected an electrical fault on the reverse warning signal (reversing buzzer) circuit, specifically that the current draw is exceeding 2500 mA (2.5 Amps) or there is a direct short circuit.

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• Fendt 300 Vario (COM III)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III)
• Fendt 800 Vario (COM III)
• Fendt 900 Vario (COM III)

1. 1

   Locate the reverse warning buzzer (component designation H007), which is typically mounted at the rear of the tractor.

2. 2

   Disconnect the electrical connector from the buzzer, turn the tractor on, and engage reverse; if the fault code changes to an 'open circuit' or clears, the buzzer itself has an internal short.

3. 3

   If the fault remains active with the buzzer disconnected, trace the wiring from the H007 buzzer back to the A050 ECU to inspect for pinched wires, melted insulation, or chafing against the tractor chassis.

4. 4

   Use a multimeter to measure the resistance across the pins of the disconnected buzzer; a reading of near 0 ohms confirms an internal short.

1. 1

   Disconnect battery

   Turn off the tractor and disconnect the battery ground cable to prevent electrical spikes.

2. 2

   Repair wiring harness

   If the wiring harness is damaged, repair the shorted section using heat-shrink butt connectors and re-loom the harness to protect it from future chafing.

3. 3

   Remove faulty buzzer

   If the buzzer is internally shorted, unbolt the faulty H007 reverse buzzer from its mounting bracket.

4. 4

   Install replacement buzzer

   Install the replacement reverse warning buzzer and secure the mounting hardware.

5. 5

   Reconnect electrical plug

   Reconnect the electrical plug, ensuring the weather seal is intact and the connector clicks into place.

6. 6

   Reconnect battery

   Reconnect the battery ground cable.

7. 7

   Verify repair

   Start the tractor, clear the stored fault codes via the terminal, and shift into reverse to verify that the buzzer sounds and the 04.1.79 code does not return.