New Holland 50 – TCU / TRANS / UCM: Park Brake Is Powered Off When in Park

The Transmission Control Unit (TCU) has detected a loss of power in the park brake circuit when the machine is in the park position. The park brake is spring-applied and hydraulically released, requiring hydraulic pressure controlled by an electric solenoid to release. When in park, the solenoid should be de-energized to allow the spring to engage the brake. This loss of power in the circuit may prevent the park brake from engaging properly, leading to potential movement of the machine when it should be stationary.

• T8.330
• T8.360
• TG210
• TG230
• TG255
• TG285
• Magnum
• L180
• L185
• L230
• L190
• C185
• C190
• LT185.B
• B95B
• B110B

1. 1

   Verify battery and system voltage is fully charged (above 12.6V) and that all primary power and ground connections to the chassis are clean and tight.

2. 2

   Visually inspect the wiring harness and connectors leading to the park brake solenoid for damage, corrosion, abrasion, or loose connections (especially the connector at the solenoid on T8 tractors).

3. 3

   With the key on and park brake disengaged, use a multimeter to check for voltage at the park brake solenoid's electrical connector.

4. 4

   Disconnect the solenoid and measure resistance across its terminals (a typical good coil reads between 8 and 12 ohms; infinite resistance indicates an open circuit, near zero indicates a short).

5. 5

   Check the park brake pressure switch for continuity, as a faulty switch can cause a disagreement between the solenoid's state and expected pressure (applicable to some skid steers).

1. 1

   Prepare machine safely

   Park the machine on a level surface, lower all attachments to the ground, and shut down the engine. Engage all safety locks and disconnect the battery. Safely raise and block the machine if required for access.

2. 2

   Locate the park brake solenoid

   On L-Series skid steers, locate the solenoid on the hydraulic valve block between the reservoir and right hydro motor (access may require removing a skid plate from underneath the machine). On North American T8/TG/Magnum tractors, locate it on top of the transmission under the cab (access can be difficult and may require removing wheels or the cab air filter housing). On European tractors, locate it on the right side of the transmission in front of the rear axle.

3. 3

   Remove the faulty solenoid

   Carefully disconnect the electrical connector. Clean the area around the solenoid to prevent hydraulic contamination. Using an appropriate wrench, unscrew the solenoid valve from the valve block (be prepared for hydraulic fluid to leak).

4. 4

   Install the new solenoid

   Lubricate the O-rings on the new solenoid with clean hydraulic fluid. Screw the new solenoid into the valve block and tighten to the manufacturer's specified torque. Reconnect the electrical connector.

5. 5

   Reassemble and test

   Re-install any components removed for access (skid plates, wheels, etc.). Reconnect the battery, start the machine, and allow it to warm up. Clear the fault code using the diagnostic menu or service tool, and test the park brake function to ensure it engages and disengages correctly.