Case IH 519050-14 - BCM – BCM: ATC temperature increase switch - invalid input voltage

The Automatic Temperature Control (ATC) system relies on this switch to command the climate control system to raise the cab temperature. An "invalid input voltage" indicates that the signal returning from the switch to the controller is outside the expected electrical parameters. This typically points to an open circuit, a short to ground, a short to power (B+), or an internal failure of the switch/potentiometer itself.

• MAGNUM AFS Connect
• Steiger AFS Connect
• Optum AFS Connect

1. 1

   Inspect the ATC control panel and the temperature increase switch/knob for physical damage, sticking, or liquid spills that may have shorted the internal contacts.

2. 2

   Check the wiring harness between the ATC switch panel and the BCM. Test the signal wire for continuity to ensure there is no open circuit.

3. 3

   Use a multimeter to test the switch signal wire for a short to ground or a short to power (B+).

4. 4

   Inspect the connectors at both the BCM and the ATC module. Look for pushed-out pins, moisture, or corrosion, which are common causes of invalid voltage readings.

5. 5

   Verify that the switch is receiving the correct reference voltage (typically 5V or system voltage, depending on the specific pinout) from the controller.

1. 1

   Power Down

   Turn off the key switch and disconnect the tractor's battery to prevent electrical shorts during the repair.

2. 2

   Access the Module

   Remove the necessary interior cab trim panels to access the ATC control panel and the BCM (often located in the side console or roof, depending on the exact cab layout).

3. 3

   Inspect and Clean

   Disconnect the wiring harness from the ATC control module. Inspect the connector pins. Clean any corrosion and ensure all pins are seated tightly.

4. 4

   Harness Repair (If Applicable)

   If the diagnostic checks revealed a broken wire or short in the harness, splice in a new wire or replace the damaged connector section.

5. 5

   Replace the Component

   If the wiring harness tests good, the fault lies within the ATC control module or the switch itself. Remove the mounting screws and replace the faulty ATC control module/switch assembly.

6. 6

   Reassembly

   Reconnect the wiring harness and reinstall the cab trim panels.

7. 7

   Clear Codes

   Reconnect the battery. Turn the key to the ON position and use the Electronic Service Tool (EST) or the AFS Pro display to clear the stored fault codes. Test the ATC system to ensure the temperature controls respond correctly.