Case IH 1079.04 - ACML – ACML: Sensor Supply Voltage Low

The control module has detected that its 5-volt sensor supply circuit has dropped below the acceptable operating threshold (typically measuring less than 4.44V to 4.8V). This condition is caused by a direct short to ground (0V) somewhere in the 5V reference circuit.

• VESTRUM CVX
• Case IH Magnum Series
• Case IH Maxxum Series
• Case IH Puma Series
• Case IH Steiger Series

1. 1

   Turn the key ON and verify that code 1079.04 is currently active.

2. 2

   Sensor Isolation (Drop-out Test): Disconnect armrest sensors (e.g., hand throttle, joystick sensors, hitch position dials) one at a time while monitoring the 5V reference circuit with a multimeter. If the voltage jumps back up to ~5V when a specific sensor is unplugged, that sensor is internally shorted.

3. 3

   Harness Check: If all sensors are disconnected and the circuit is still shorted to 0V, disconnect the main harness from the ACML. Measure the resistance of the 5V supply wire to a known good ground. If there is continuity, the wiring harness is pinched or chafed against the chassis.

4. 4

   Module Check: If the harness tests good (no short to ground) and the sensors are good, but the ACML still fails to output 5 volts from its supply pins, the ACML's internal voltage regulator has failed.

1. 1

   Power Down

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

2. 2

   Expose the Armrest

   Remove the plastic covers and trim pieces on the Multicontroller armrest to access the ACML and the internal wiring harness.

3. 3

   Repair the Faulty Component

   If a sensor is shorted: Unbolt the faulty potentiometer/switch from the armrest console and install a replacement. If the harness is shorted: Trace the 5V wire to find the chafed section. Repair the wire using OEM-approved heat-shrink butt connectors, or replace the affected armrest sub-harness. If the ACML is faulty: Disconnect the multi-pin connectors from the ACML. Unbolt the module from its mounting bracket and remove it. Install the new ACML and reconnect the harnesses.

4. 4

   Reassemble and Test

   Reconnect the battery. Turn the key ON and use the tractor's diagnostic display or a service tool to clear the inactive 1079.04 code.

5. 5

   Calibrate

   If the ACML or a major armrest sensor was replaced, perform the armrest/joystick calibration procedures as prompted by the tractor's display.