Case IH 16127 – ATC (Automatic Temperature Control) module: High pressure switch (-) input shorted to power

The system has detected that the negative (-) input circuit coming from the air conditioning (A/C) high-pressure switch has a short circuit to a 12V power source.

• Puma/Mid Range Magnum
• Maxxum
• Puma Series (e.g., 140, 145, 150, 165, 175, 180, 195, 210, 225, T6000/SWB PUMA)
• Steiger Series
• Magnum Series
• MX/TG Series
• Farmall Series (40, 45, 50 with Cab and CVT)

1. 1

   Verify A/C system charge to ensure the system is properly charged with refrigerant (the high-pressure switch should be closed if correctly charged).

2. 2

   Inspect the wiring harness, specifically the negative branch of the switch wiring, for melted insulation or chafing that could expose the wire to a 12V power source.

3. 3

   Check connectors X755, X225, X695, and X024 for damage, corrosion, or internal shorts.

4. 4

   Test the ATC module for an internal failure if the wiring and connectors are intact.

1. 1

   Test the Circuit

   Disconnect the A/C high-pressure switch. Use a multimeter to check the negative (-) input wire for voltage. If voltage is present, there is a short to power in the harness.

2. 2

   Inspect and Repair Wiring/Connectors

   Trace the wiring harness back to the ATC module. Disconnect and inspect connectors X755, X225, X695, and X024. Look for bent pins, corrosion, or crossed wires. Repair or replace any damaged sections of the wiring harness.

3. 3

   Test the High-Pressure Switch

   If the wiring is good, test the high-pressure switch for internal failure. If the switch is faulty, recover the A/C refrigerant using an approved machine, replace the switch, and recharge the system to OEM specifications.

4. 4

   Replace the ATC Module

   If the wiring harness, connectors, and high-pressure switch are all functioning correctly, the fault lies within the ATC module. Replace the ATC module and clear the fault codes to verify the repair.