Massey Ferguson 42 – Armrest Autotronic 5: FingerTIP 4 - short circuit to 12V

The signal wire for the 4th spool valve switch (X109) is receiving a voltage that is too high. This happens when the signal circuit is shorted directly to a 12V power source, or if the switch has suffered an internal short.

• 5600 Series
• 6600 Series
• 6700 Series
• 7600 Series
• 7700 Series
• 8600 Series
• 8700 Series

1. 1

   Remove the armrest cover and visually inspect the wiring harness leading to the FingerTIP 4 switch (X109) for pinched wires, chafed insulation, or rubbing against the metal seat frame.

2. 2

   Unplug the switch and inspect the connector pins for moisture, corrosion, or bent pins that could be bridging the 12V reference/supply power to the signal return pin.

3. 3

   With the tractor key ON, disconnect the FingerTIP 4 switch to isolate it. If the code changes from AR 42 to AR 41, the switch is internally shorted. If it remains AR 42, the short to 12V is located in the wiring harness.

1. 1

   Safety First

   Turn off the tractor ignition and disconnect the negative battery terminal to prevent electrical spikes during the repair.

2. 2

   Access the Switch

   Remove the retaining screws securing the top plastic bezel/cover of the armrest console to expose the underside of the FingerTIP switches.

3. 3

   Disconnect

   Locate the 4th FingerTIP switch (X109) and carefully unplug its electrical connector.

4. 4

   Harness Repair

   If your diagnostics pointed to a harness short, trace the wire back to the Autotronic 5 module, locate the damaged insulation, and repair it using solder and marine-grade heat shrink.

5. 5

   Remove the Switch

   If the switch is the culprit, depress the retaining tabs or remove the mounting screws holding the switch into the armrest panel and pull it out.

6. 6

   Install the New Part

   Push the new OEM FingerTIP switch into the console until it clicks into place.

7. 7

   Reassemble

   Reconnect the electrical plug, ensuring the locking tab engages. Reinstall the armrest console cover.

8. 8

   Clear Codes and Test

   Reconnect the battery. Turn the ignition ON, navigate to the error code menu on the dashboard or Datatronic screen, and clear the inactive fault codes. Start the tractor and test the 4th auxiliary remote to ensure proper proportional control.