Massey Ferguson 71 – Armrest Autotronic 5: Hand throttle (Component X122) - Short circuit to 0 V

The control module is receiving a 0-volt signal from the hand throttle potentiometer, indicating that the signal wire is either shorted directly to ground or the potentiometer has failed internally and is pulling the voltage to zero.

• 8650
• 8660
• 8670
• 8680
• 8690
• 8727
• 8730
• 8732
• 8735
• 8737
• 8740
• 7614-7626
• 7714-7726
• 6445-6499
• 6612-6616
• 6712S-6718S
• 5608-5613
• 5709-5713S
• 7400 Series
• 8400 Series

1. 1

   Inspect the wiring harness running from the hand throttle potentiometer (X122) to the Armrest Autotronic 5 controller for chafed insulation, pinched wires, or areas rubbing against the metal frame.

2. 2

   Disconnect the hand throttle potentiometer and inspect the pins for corrosion, moisture, or bent terminals that could bridge the signal wire to the ground wire.

3. 3

   With the sensor disconnected, turn the key ON and use a multimeter to check the signal wire on the harness side to isolate the short. If the short to ground is gone, the potentiometer has failed internally. If present, the harness is damaged.

1. 1

   Disconnect Power

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

2. 2

   Access the Component

   Remove the necessary trim panels and covers on the armrest console to expose the hand throttle assembly (Component X122).

3. 3

   Remove the Faulty Sensor

   Unplug the electrical connector from the hand throttle potentiometer. Unbolt or unclip the potentiometer switch from the throttle lever mechanism.

4. 4

   Install the New Part

   Mount the replacement hand throttle potentiometer switch into the armrest assembly and secure it. Reconnect the electrical harness.

5. 5

   Reassembly

   Reinstall the armrest console covers and trim panels.

6. 6

   Calibration

   Reconnect the battery. Turn the key ON and clear the stored AR 71 / D 170 fault codes from the Armrest and Instrument Panel modules. You may need to perform a hand throttle potentiometer calibration via the tractor's diagnostic menu so the Autotronic 5 controller can learn the new 0-100% voltage sweep.