New Holland ATC 134 – ATC (Automatic Temperature Control) Controller: Low pressure switch open for > 1 minute

The Automatic Temperature Control (ATC) controller has detected that the air conditioning system's low-pressure cut-out switch has remained in an open state for a cumulative 60 seconds. This is a protective measure that shuts down the A/C compressor to prevent damage when the system pressure drops below safe operating levels (typically due to low refrigerant).

• T5 series
• T6 series
• T7 series
• T8 series
• T9 series
• TG210
• TG230
• TG255
• TG285
• TJ275
• TJ325
• TJ375
• TJ425
• TJ450
• TJ500
• CR6.80 to CR9.90
• CR920-CR980
• CX840-CX8090
• FR series
• HW/H8000 series
• L223
• L225
• L230
• C232
• C238

1. 1

   Check A/C System Charge: Connect a manifold gauge set to the A/C service ports to check the static and running refrigerant pressures. The most common cause of this code is an incorrect charge (low refrigerant) due to a leak.

2. 2

   Inspect Wiring and Connectors: If the system pressure is within specification, visually inspect the wiring harness and all connectors between the A/C low-pressure switch and the ATC controller. Look for chafed wires, corrosion, or disconnected plugs.

3. 3

   Test the Switch: Test the low-pressure switch for continuity. If the system has proper pressure but the switch remains open, the switch has failed internally.

1. 1

   Address Refrigerant Leaks (If Applicable)

   If gauge testing reveals low pressure, use an electronic leak detector or UV dye to locate the leak. Recover the remaining refrigerant using an approved A/C recovery machine, repair the leak, pull a vacuum, and recharge the system to the exact OEM weight specification.

2. 2

   Repair Wiring (If Applicable)

   If the harness is damaged, repair or replace the affected wiring between the switch and the ATC module.

3. 3

   Replace the Low-Pressure Switch

   Locate the low-pressure switch on the A/C low side line. Disconnect the weather-sealed electrical connector. Unthread the switch from the service port (most modern New Holland ports have a Schrader valve behind the switch, meaning you can often unthread it without discharging the system, but verify your specific model's configuration first). Thread the new switch onto the fitting and tighten securely. Reconnect the electrical harness.

4. 4

   Clear Codes

   Cycle the key and use your diagnostic tool to clear the ATC 134 fault code. Run the machine and verify the A/C compressor engages and the cab cools properly.