New Holland 134 – ATC / Engine: A/C Low Pressure Switch and Decelerator Circuit Analysis

This fault code has two distinct meanings depending on the controller logging it. When logged by the Automatic Temperature Control (ATC) module, it indicates the A/C low-pressure switch has remained open for a cumulative 60 seconds, shutting down the compressor to prevent damage from low refrigerant or poor oil circulation. When logged by the Engine controller, it indicates the decelerator pedal position potentiometer voltage is too low, suggesting an open circuit, short to ground, or failed sensor.

• T8 Series
• T5 Series
• T6 Series
• T7 Series
• Combines
• Forage Harvesters

1. 1

   If logged by ATC (A/C issue): Verify A/C refrigerant charge using a manifold gauge set to check static and operating pressures.

2. 2

   If logged by ATC (A/C issue): Inspect wiring harness and connectors at the low-pressure switch, and the junction where the main engine harness meets the cab harness, for corrosion or damage.

3. 3

   If logged by ATC (A/C issue): Test the low-pressure switch with a multimeter for continuity (should be closed/near 0 Ohms at rest with sufficient static pressure).

4. 4

   If logged by Engine (Decelerator issue): Check the decelerator pedal sensor wiring for damage, and verify the 5-volt reference supply and ground connections.

5. 5

   If logged by Engine (Decelerator issue): Test the decelerator sensor's output voltage through its full range of motion.

1. 1

   Recover Refrigerant

   If not already done, the A/C system's refrigerant must be safely and legally recovered by a certified technician using appropriate equipment.

2. 2

   Replace the Low-Pressure Switch

   Once the system is evacuated, unscrew the old pressure switch from its port on the A/C line. It is advisable to have the new switch ready to install promptly to minimize the ingress of moisture into the system.

3. 3

   Install New Switch

   Lubricate the O-ring on the new switch with the correct type of refrigerant oil and thread it into place. Tighten to the manufacturer's specified torque, being careful not to overtighten.

4. 4

   Evacuate and Recharge System

   Connect a vacuum pump to the A/C system to remove all air and moisture. This process should be performed for a minimum of 30-60 minutes.

5. 5

   Recharge with Refrigerant

   After evacuation, recharge the system with the manufacturer-specified type and quantity of refrigerant.

6. 6

   Test System Operation

   Start the tractor, turn on the air conditioning, and verify that the compressor engages and the system cools properly. Check for leaks and monitor operating pressures.

7. 7

   Clear Fault Codes

   Use a diagnostic tool to clear the ATC 134 fault code.