New Holland TMF 120 – TMF Controller: Electro Hydraulic Remote top link switch is stuck on

The controller is receiving a continuous, uninterrupted "ON" signal from the external top link switch. This condition is usually caused by a switch that is physically jammed by debris, internally shorted, or a wiring harness that has shorted to a voltage source.

• T7 Series
• T7.175
• T7.190
• T7.230
• T7.245
• T7.270
• T8 Series
• T8000 Series
• T8010
• T8020
• T8030
• T8040
• T8050
• TG Series
• T7000 Series
• T7030
• T7040
• T7050
• T7060

1. 1

   Inspect the external top link switch on the rear fender extension. Look for packed dirt, mud, or physical damage that might be physically holding the button in the depressed position.

2. 2

   Disconnect the wiring harness from the back of the fender switch. Turn the key on and check if the TMF 120 code changes to an 'open circuit' code or clears. If the code goes away, the switch is internally shorted and must be replaced.

3. 3

   Using a multimeter, test the disconnected switch. It should only show continuity when the button is actively pressed. If it shows continuity while at rest, the switch has failed.

4. 4

   If disconnecting the switch does not clear the 'stuck on' fault, inspect the wiring harness running from the fender to the TMF controller. Look for pinched wires, chafing, or melted insulation causing a short-to-power (12V).

5. 5

   Check the switch connector pins for water ingress or corrosion, which can bridge the terminals and cause a false signal.

1. 1

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

2. 2

   Locate the faulty top link switch on the rear fender extension panel.

3. 3

   Reach behind the fender panel and depress the locking tab to disconnect the electrical pigtail from the switch.

4. 4

   Remove the retaining nut or depress the plastic retaining clips holding the switch body to the fender panel.

5. 5

   Push the old switch out of the rectangular mounting hole.

6. 6

   Clean the mounting hole and surrounding fender area of any dirt or debris.

7. 7

   Snap or bolt the new OEM switch into the fender panel.

8. 8

   Apply a small amount of dielectric grease to the electrical connector to prevent future moisture ingress, then plug it into the new switch.

9. 9

   Reconnect the battery, turn the ignition on, and clear the stored TMF fault codes.

10. 10

    Test the external 3-point hitch controls to verify proper operation.