Case IH 113 – ATC (Automatic Temperature Control): Outlet sensor open or shorted to power

The system has detected that the electrical circuit for the HVAC outlet temperature sensor is either broken (open circuit) or is receiving unintended voltage (shorted to a 12V power source). This sensor monitors the temperature of the air coming out of the HVAC vents into the cab to regulate blower speed and climate control.

• Case IH Magnum 235 - 340 (Series 4)
• Case IH Puma series (e.g., Puma 125, 140, 165, 180, 195, 210, 225 CVX)

1. 1

   Visual Inspection: Locate the outlet temperature sensor in the cab's HVAC ducting/louvers. Inspect the sensor connector (X753) for backed-out pins, corrosion, or moisture.

2. 2

   Wiring Harness Check (Open Circuit): Disconnect the sensor and use a multimeter to check for continuity on the signal and ground wires between the sensor connector and the ATC module. A broken wire will cause the "open" condition.

3. 3

   Wiring Harness Check (Short to Power): With the key ON, test the sensor signal wire with a multimeter to ensure it is not receiving 12V from a rubbed or chafed wire in the harness.

4. 4

   Sensor Resistance Test: Measure the resistance across the sensor's pins. If the multimeter reads 'OL' (out of limits/infinite resistance), the sensor has failed internally and is causing the open circuit.

1. 1

   Power down machine

   Power down the machine and turn the battery disconnect switch to the OFF position.

2. 2

   Access HVAC ducting

   Access the HVAC ducting inside the cab where the outlet temperature sensor is mounted.

3. 3

   Disconnect sensor

   Disconnect the X753 wiring harness connector from the sensor.

4. 4

   Repair wiring harness

   If the diagnostic checks revealed damaged wiring, repair the harness using OEM-approved splice connectors and heat shrink.

5. 5

   Replace sensor

   If the sensor failed the resistance test, unclip or unthread the faulty sensor from the HVAC duct and install the replacement sensor.

6. 6

   Reconnect harness

   Reconnect the X753 wiring harness.

7. 7

   Clear fault codes

   Restore battery power, turn the key ON, and use a Case IH diagnostic scan tool (or compatible software like Jaltest) to clear the inactive fault codes from the ATC module.

8. 8

   Verify operation

   Run the HVAC system and verify that the blower speed adjusts correctly based on the outlet temperature.