CLAAS 752Ch – MFA: Engine Speed Contact Signal Fault

The Multifunction Armrest (MFA) module (A100) has detected an abnormal voltage signal from the engine speed contact (S189). The signal may be too high, too low, or incoherent, which indicates a potential short circuit, open circuit, or an erratic signal from the engine speed sensor.

• Axion 810
• Axion 850
• Arion 510-640
• Axion
• Arion

1. 1

   Inspect electrical connectors at the engine speed sensor (S189) and the MFA armrest multifunction module (A100) for corrosion, dirt, moisture, or damaged pins.

2. 2

   Check the wiring harness between the engine speed sensor and the MFA module for visible damage, chafing, cuts, or pinch points.

3. 3

   Test the wiring harness for continuity, open circuits, and short circuits to ground or power using a multimeter.

4. 4

   Verify sensor functionality by monitoring the engine speed signal in real-time using the CLAAS Diagnostic System (CDS).

1. 1

   Locate components

   Locate the engine speed contact (S189), which is likely the primary engine speed sensor (B231) on the engine block, and the MFA module (A100) inside the main armrest console.

2. 2

   Repair wiring or connectors

   If diagnostic checks reveal damaged wiring or faulty connectors between the sensor and the MFA module, repair or replace the affected harness sections.

3. 3

   Replace engine speed sensor

   If the sensor is determined to be faulty, unbolt and remove the old sensor. Install the new sensor, ensuring the correct air gap is set if applicable.

4. 4

   Replace MFA module

   If the MFA module is diagnosed as the source of the fault, disconnect and remove it from the armrest. Install the replacement module and configure it using the CLAAS Diagnostic System (CDS).