Case IH 33 – Hitch Controller / Electronic Draft Control (EDC) microprocessor: Draft Control Potentiometer Open Circuit Or Short To Ground

The electronic draft control (EDC) system is receiving an abnormal voltage signal from the draft control sensor (potentiometer). The controller detects that the signal is either completely lost due to a broken wire/disconnected plug (open circuit) or the signal wire is touching the tractor's chassis (short to ground).

• MXM
• Case IH MXM Series (MXM 120, 130, 140, 155, 175, 190)
• Case IH MX / MX-C Series (MX80C through MX170)
• Case IH CX Series (CX50 through CX100)
• Case IH Magnum & TG Series
• Case IH Farmall Series (115U Pro, 90A)

1. 1

   Visual Inspection: Locate the hitch draft control potentiometer connector (identified in some manuals as connector X-037). Check that the connector is tight and free of dirt, moisture, or bent pins.

2. 2

   Check for Short to Ground: Using a multimeter, test the signal wire between the sensor connector and the EDC controller. If continuity to ground is indicated, the harness is shorted and must be repaired.

3. 3

   Check for Open Circuit: Wiggle the harness and connectors while checking for continuity between the sensor pin and the controller pin. If there is infinite resistance, there is a break in the wire.

4. 4

   Check Reference Voltage: Ensure the sensor is receiving its standard 5-volt reference and a solid ground from the microprocessor.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to protect the EDC modules.

2. 2

   Harness Repair (If Applicable)

   If the diagnostic checks revealed a short or open circuit in the wiring, repair or replace the affected section of the hitch control harness.

3. 3

   Sensor Replacement

   If the wiring and reference voltage are good, the potentiometer itself has failed internally. Unbolt the faulty draft control potentiometer from the 3-point hitch lift linkage assembly and install the new OEM sensor.

4. 4

   Reconnection

   Plug the harness back into the new sensor, ensuring the weather-tight seal clicks into place.

5. 5

   Hitch Calibration

   Because the EDC controller relies on precise voltage variations to determine hitch position and draft load, you must perform a hydraulic lift autocalibration (3-point hitch calibration) after replacing the potentiometer so the module can learn the new sensor's upper and lower voltage limits.