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ATC 128

New Holland ATC 128 – ATC (Automatic Temperature Control) module: High pressure switch (-) input shorted to ground.

Issue description

The Automatic Temperature Control (ATC) module has detected a short-to-ground condition on the negative (-) side of the air conditioning high-pressure switch circuit. Because the A/C high-pressure switch is a normally closed switch, the short could technically be present on either wire leading to the switch. This fault will typically disable the A/C compressor clutch to protect the system.

Applies to these machines

  • T4
  • T5
  • T6
  • T7
  • T8
  • T9
  • TG series
  • TG210
  • TG245
  • TJ series
  • TJ275
  • TJ450
  • TV series
  • TV140
  • CR series
  • CR9090
  • CX series
  • CX8080
  • CX8090
  • TC
  • TX
  • FX
  • U80
  • LV80
  • W-series

Check the cause

  1. Visually inspect the wiring harness, the high-pressure switch connector, and the ATC controller for physical damage, rubbing, or melted insulation.

  2. If damage to the connectors or wiring is found, repair or replace the harness, clear all fault codes, and return the unit to operation.

  3. Check for a short circuit at the switch: Turn the key switch to the ON position, disconnect the harness connector (e.g., C175) at the high-pressure switch, and measure the voltage/continuity on the pins to ground to determine if the short is internal to the switch or located within the wiring harness leading back to the ATC module.

Repair steps

  1. Turn the machine off and ensure the key switch is in the OFF position.

  2. Locate the A/C high-pressure switch, which is installed on the high-pressure side of the A/C line (often near the receiver drier or condenser).

  3. Disconnect the wiring harness from the switch.

  4. Unscrew the faulty high-pressure switch from the A/C line.

    Many CNH high-pressure switches are mounted on a Schrader valve fitting, meaning the switch can be unthreaded without discharging the A/C system's refrigerant. Verify your specific machine's fitting before removal to avoid venting refrigerant.

  5. Thread the new OEM high-pressure switch onto the fitting (standard thread size is M10 x 1.25) and tighten securely.

  6. Reconnect the wiring harness connector.

  7. Clear the ATC 128 fault code from the ATC module using the cab display or a diagnostic tool.

  8. Start the machine and engage the A/C to verify the compressor clutch engages and the code does not return.

Parts you might need

(5)

  • A/C High-Pressure Switch (Normally Closed)

    87627132

    Fits most T4, T5, T6, T7, T8 tractors and CX/CR combines. Replaces 87349491, 87038394, 82018884, 82026899.

  • A/C High-Pressure Switch (Normally Closed)

    87000227

    Fits T8010–T8040 and TG210–TG245 tractors. Replaces 284273A1, 284273A2, 87775423.

  • A/C High-Pressure Switch (Normally Closed)

    87366056

    Fits TX, TC, and FX Harvesters. Replaces 84012145, 03247432.

  • A/C High-Pressure Switch (Normally Closed)

    232948A1

    Fits New Holland industrial equipment (U80, LV80, W-series loaders).

  • A/C High Pressure Switch Assembly

    87305163

    General New Holland A/C High Pressure Switch Assembly.

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