Case IH 34 – PTO Controller: PTO Solenoid Coil Failed Short or Wiring Shorted to Ground

The PTO solenoid coil has failed short (the electrical resistance is too low) or the wiring circuit from the controller to the PTO solenoid is shorted to ground. When this condition is detected, the controller disables the PTO to prevent electrical damage, resulting in a PTO that will not engage.

• MX Maxxum
• MX210
• MX220
• MX230
• MX255
• MX285
• MX80C through MX170
• Maxxum
• Puma
• Farmall

1. 1

   Verify the alternator is outputting correctly from the 'W' terminal (if applicable), as a missing RPM signal will prevent PTO engagement entirely.

2. 2

   Remove the controller cover from the rear of the tractor and disconnect the black connector (C057) from the PTO controller.

3. 3

   Measure the resistance between pins C057-5 and C057-4 on the harness side. Normal resistance is 6.0 to 6.8 ohms at 25°C (70°F).

4. 4

   If resistance is too low, disconnect the harness directly at the PTO solenoid (Connector C159) and test the solenoid's resistance directly to isolate the short.

5. 5

   If the solenoid tests within 6.0 - 6.8 ohms, repair the shorted wiring harness. If it tests below spec, replace the internally shorted solenoid coil.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the Solenoid

   Locate the PTO control valve assembly, typically mounted on the rear transmission/PTO housing.

3. 3

   Disconnect Wiring

   Unplug the electrical connector (C159) from the faulty PTO solenoid.

4. 4

   Remove the Coil

   Remove the retaining nut at the end of the solenoid valve stem. Slide the old solenoid coil off the cartridge. (Note: If replacing the entire valve assembly rather than just the coil, unscrew the cartridge from the manifold block. Have a catch pan ready for a small amount of hydraulic fluid).

5. 5

   Install New Part

   Slide the new PTO solenoid coil onto the valve stem and tighten the retaining nut.

6. 6

   Reconnect

   Plug the electrical connector back into the solenoid.

7. 7

   Test

   Reconnect the battery, start the tractor, and clear the stored fault codes using the instrumentation display. Engage the PTO switch to verify proper operation.