Case IH 16122 – ATC (Automatic Temperature Control) Module / HVAC Control Unit: Mode select potentiometer open or shorted to power

This code indicates a circuit failure related to the HVAC Mode Select Potentiometer (the dial on the climate control panel that dictates air distribution). The control module has detected that the signal voltage from this potentiometer is out of its normal operating range—specifically, the circuit is either completely open or shorted directly to a power source.

• Puma/Mid Range Magnum
• Maxxum
• Puma Series
• Magnum Series
• Axial-Flow Combines

1. 1

   Monitor live data via H-Menu diagnostics or EST to check the Mode Select Potentiometer voltage (look for 0V or steady 5V+ while turning the dial)

2. 2

   Visually inspect the wiring harness and connector at the back of the HVAC control panel for backed-out pins, corrosion, or chafing

3. 3

   Perform a voltage and continuity test to verify 5V reference and ground are present at the control panel connector

4. 4

   Check the signal wire for continuity between the control panel connector and the ATC module, and test for a short to 12V power

5. 5

   If wiring tests good (proper 5V reference, good ground, no shorts), conclude the failure is internal to the potentiometer on the control panel

1. 1

   Disconnect Power

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

2. 2

   Remove Trim

   Carefully pry off or unscrew the cab trim bezels surrounding the HVAC control panel (typically located on the right-hand console or B-pillar, depending on the tractor/combine model).

3. 3

   Extract the Panel

   Remove the retaining screws holding the HVAC control panel in place.

4. 4

   Disconnect Harness

   Pull the panel forward and carefully unplug the electrical harness connectors from the rear of the unit.

5. 5

   Install New Panel

   Connect the wiring harness to the replacement HVAC control panel.

6. 6

   Reassembly

   Secure the new panel with the retaining screws and snap the interior trim bezels back into place.

7. 7

   Clear Codes

   Reconnect the battery. Turn the key to the ON position. Use the H-Menu or EST to clear the inactive 16122 fault code. Test the mode dial to ensure the actuator doors physically change the airflow direction.