Case IH 135 – ATC (Automatic Temperature Control): Clutch output fault (overcurrent, short to ground)

The controller has detected an electrical current draw that exceeds the maximum allowable limit on the A/C compressor clutch circuit, or it has detected a direct short to the chassis ground. This is typically caused by an internally shorted A/C clutch coil (melted windings) or a chafed power wire touching the engine block or frame.

• STX Steiger
• MX Magnum series
• TG series
• Steiger
• Puma
• Maxxum
• Axial-Flow 5088
• Axial-Flow 6088
• Axial-Flow 7088
• Axial-Flow 7230
• Axial-Flow 8230
• Axial-Flow 9230

1. 1

   Visual Wiring Inspection: Trace the wiring harness from the A/C compressor clutch back to the ATC module/relay. Look for pinched wires, melted insulation, or areas where the wire may have rubbed against the engine block, belts, or frame, causing a direct short to ground.

2. 2

   Clutch Coil Resistance Test: Disconnect the electrical connector at the A/C compressor clutch. Using a multimeter set to Ohms, measure the resistance across the clutch coil terminals (or from the power terminal to the compressor body ground). A healthy 12V clutch coil typically reads between 3 to 5 ohms. A reading near 0 ohms (e.g., 0.4 ohms) confirms the coil is internally shorted to ground.

3. 3

   Circuit Isolation Test: With the clutch disconnected, turn the key ON and command the A/C on. If the ATC 135 code immediately returns or a fuse/breaker trips, the short is in the wiring harness or the A/C clutch relay. If the code does not return (or changes to an open circuit code), the short is isolated to the compressor clutch coil itself.

1. 1

   If the wiring harness is shorted: Disconnect battery and locate damage

   Disconnect the machine's battery. Locate the chafed or melted section of the A/C clutch power wire.

2. 2

   If the wiring harness is shorted: Repair and reroute wire

   Cut out the damaged section and splice in a new wire using solder and marine-grade heat-shrink tubing. Reroute the harness and secure it with zip-ties away from moving pulleys and hot exhaust components.

3. 3

   If the A/C Compressor Clutch Coil is shorted: Disconnect battery and remove belt

   Disconnect the battery. Release the tension on the serpentine/drive belt and remove the belt from the A/C compressor pulley.

4. 4

   If the A/C Compressor Clutch Coil is shorted: Remove clutch hub

   Disconnect the A/C clutch electrical connector. Remove the center retaining bolt on the A/C compressor clutch hub. Use a clutch hub puller tool to carefully remove the front clutch plate. Be careful not to lose the small spacing shims inside the hub.

5. 5

   If the A/C Compressor Clutch Coil is shorted: Remove pulley and shorted coil

   Remove the snap ring retaining the pulley and slide the pulley off the compressor snout. Remove the final snap ring holding the electromagnetic coil in place and remove the shorted coil.

6. 6

   If the A/C Compressor Clutch Coil is shorted: Install new coil and pulley

   Install the new A/C clutch coil, ensuring the alignment pin seats into the compressor body, and secure it with the snap ring. Reinstall the pulley and its snap ring.

7. 7

   If the A/C Compressor Clutch Coil is shorted: Reinstall clutch hub and check air gap

   Reinstall the clutch hub with the original shims. Torque the center bolt to OEM specifications. Check the clutch air gap with a feeler gauge (typically 0.016" - 0.030" depending on the Sanden/Denso compressor model). Add or remove shims as necessary.

8. 8

   If the A/C Compressor Clutch Coil is shorted: Final reassembly and code clearing

   Reinstall the drive belt, reconnect the electrical connector, and clear the ATC 135 fault code using the cab display or a diagnostic tool.