Case IH 16131 - ATC – ATC (Automatic Temperature Control) module / controller: Low pressure switch (+) input shorted to ground.

The positive input signal wire coming from the Air Conditioning (A/C) low-pressure switch is short-circuited to a ground source. The low-pressure switch is a safety device that monitors refrigerant pressure on the suction side of the A/C circuit. If the pressure drops below a safe threshold (indicating a leak or low charge), the switch cuts power to the compressor clutch to prevent the compressor from overheating and seizing.

• MAXXUM T4E
• VESTRUM CVX
• Puma series (165, 180, 195, 210, 225, CVX)
• Magnum series (235, 290, 340)
• Steiger
• Maxxum
• Axial-Flow series (7230, 8230, 9230)

1. 1

   Verify that the A/C system is correctly charged with refrigerant (System Load Check).

2. 2

   Inspect the cable harness and connectors (specifically X753 and X755) between the ATC module and the low-pressure switch for chafed wires rubbing against the chassis.

3. 3

   Disconnect the low-pressure switch to see if the short-to-ground fault changes to an 'open' fault (Code 16134), which would indicate the switch itself is internally shorted.

4. 4

   Test the specific pin on the ATC module for the low-pressure switch input to rule out an internal controller failure.

1. 1

   Locate the Switch

   Locate the A/C low-pressure switch, typically mounted on the A/C system's suction/refrigerant line.

2. 2

   Test the Wiring

   With the machine off, disconnect the harness from the low-pressure switch and the ATC controller. Use a multimeter to check for continuity between the positive signal wire and the chassis ground.

3. 3

   Repair the Harness

   If continuity to ground is found in the wire, trace the harness to find the chafed or melted section and repair the wiring.

4. 4

   Replace the Switch

   If the wiring tests good, test the switch terminals. If the positive terminal is shorted to the switch housing/ground, evacuate the A/C system (if the switch does not have a Schrader valve beneath it), unthread the old switch, install the new switch, and recharge the system to factory specifications.

5. 5

   Replace the ATC Module

   If both the switch and wiring harness are in good condition, the ATC control unit has suffered an internal pin failure and must be replaced.

6. 6

   Clear Codes

   Reconnect all components, turn the key on, and clear the ATC fault codes to verify the repair.