Case IH 16126 – ATC (Automatic Temperature Control) module: High pressure switch (+) input shorted to ground

The control module is detecting a short circuit to ground on the positive signal circuit of the air conditioning (A/C) system's high-pressure switch.

• Puma/Mid Range Magnum
• Maxxum
• Puma series (140, 165, 180, 195, 210, 225)
• Magnum series (305)
• Maxxum series (115)
• Steiger series
• 2300 series combines (2366, 2388)
• SR series (SR150, SR175, SR200)
• XT series (85XT, 90XT)

1. 1

   Verify that the A/C system is correctly charged with refrigerant. If correctly charged, the high-pressure switch should close normally.

2. 2

   Inspect the wiring harness and connectors between the A/C high-pressure switch and the ATC module for rubbed, chafed, or pinched wires causing a short to ground.

3. 3

   Test the ATC module connector pins for continuity to ground, specifically checking connectors X755, X225, X695, X025, and Pin 33 on connector X755.

4. 4

   Disconnect the high-pressure switch. If the short to ground disappears on the module side of the harness, the switch itself is likely internally shorted.

1. 1

   Turn off the machine and disconnect the battery

   Ensure safety while working on the electrical system.

2. 2

   Locate the A/C high-pressure switch

   Typically mounted on the A/C receiver drier or directly on a high-pressure refrigerant line.

3. 3

   Disconnect the electrical connector

   Disconnect the electrical connector from the high-pressure switch.

4. 4

   Check the wiring harness for a short to ground

   Using a multimeter, check the wiring harness for a short to ground between the switch connector and the ATC module.

5. 5

   Repair or replace the damaged section of the harness

   Perform this if a short is found in the wiring.

6. 6

   Determine if the switch is mounted on a Schrader valve

   If the wiring tests good, the fault lies within the high-pressure switch. If it is not mounted on a Schrader valve, you must safely recover the A/C refrigerant using approved equipment before removal.

7. 7

   Remove the faulty high-pressure switch and install the replacement part

8. 8

   Reconnect the electrical connector

9. 9

   Evacuate and recharge the A/C system

   If refrigerant was recovered, evacuate and recharge the A/C system to OEM specifications.

10. 10

    Reconnect the battery, clear the fault codes, and run the A/C system

    Clear the fault codes from the ATC module and run the A/C system to verify the repair.