New Holland ENG 191 – Engine Controller (Engine ECU): A/C clutch driver shorted to ground when ON.

The control module has detected a short circuit to ground on the output circuit that provides power to the Air Conditioning (A/C) compressor clutch coil. When the system commands the A/C to turn ON, the driver circuit experiences excessive current draw because the voltage is going directly to ground instead of properly passing through the clutch coil.

• New Holland T7 Series Tractors
• New Holland T8 Series Tractors
• New Holland T9 Series Tractors
• New Holland Genesis T8 Series
• New Holland Combines
• New Holland Forage Harvesters (e.g., FR450)
• New Holland Telehandlers

1. 1

   Inspect the wiring harness from the Engine Controller to the A/C compressor clutch for chafed insulation, melted wires, or pinched areas causing a direct short to ground.

2. 2

   Disconnect the electrical connector at the A/C compressor clutch and measure the resistance of the clutch coil to ground. Zero or near-zero ohms indicates an internally shorted clutch coil.

3. 3

   Isolate the circuit by turning the key ON and commanding the A/C ON with the clutch disconnected. If the code changes to an open circuit code, the short is in the clutch; if ENG 191 remains, the short is in the wiring harness.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Repair Wiring

   If a short was found in the harness during diagnostics, cut out the damaged section of wire. Splice in a new section of wire, solder the connection, and seal it with marine-grade heat shrink. Reroute the harness and secure it with zip ties away from sharp metal edges or extreme heat sources.

3. 3

   Replace the A/C Clutch

   If the clutch coil tested as internally shorted: Remove the serpentine/drive belt from the A/C compressor. Remove the center bolt holding the clutch plate, then remove the snap rings retaining the pulley and the electromagnetic coil. Install the new A/C clutch coil, pulley, and clutch plate. (Note: On some high-hour machines, it is more cost-effective to replace the entire A/C compressor assembly).

4. 4

   Reassemble and Reconnect

   Reinstall the drive belt and reconnect the A/C clutch electrical connector. Reconnect the battery.

5. 5

   Clear Codes and Test

   Connect a diagnostic scan tool (such as the New Holland Electronic Service Tool or Jaltest) to clear the ENG 191 fault code. Start the tractor, turn on the A/C, and verify that the compressor clutch engages smoothly without the fault code returning.