Case IH 519049-14 - BCM – BCM: ATC temperature decrease switch - invalid input voltage

The control module is receiving a voltage signal from the Automatic Temperature Control (ATC) temperature decrease switch that falls outside the expected normal operating range. This condition is typically caused by an open circuit, a short to ground, a short to power within the switch's wiring harness, or an internal failure of the switch itself.

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1. 1

   Check BCM Power Supply: The BCM is located in the cab behind the operator's seat (accessed by removing a rubber liner and tray). Verify that the BCM supply fuses (F-003, F-004, F-005, F-006) are intact and providing proper voltage.

2. 2

   Inspect Wiring and Connectors: Access the back of the climate control panel and inspect the wiring harness connecting the ATC temperature decrease switch to the BCM for pinched wires, chafing, or corroded connector pins.

3. 3

   Test the Circuit: Use a multimeter to check the voltage at the switch connector. Check for continuity to ground to rule out a short-to-ground, and check for unexpected voltage to rule out a short-to-power.

4. 4

   Test the Switch: Perform a continuity test on the ATC temperature decrease switch itself. If the switch does not show proper continuity when actuated, the switch has failed internally.

1. 1

   Disconnect battery

   Power down the tractor and disconnect the negative battery cable to prevent electrical damage during the repair.

2. 2

   Access climate control console

   Remove the trim panels necessary to access the rear of the cab climate control console.

3. 3

   Disconnect switch

   Locate the ATC temperature decrease switch and carefully disconnect its electrical pigtail/connector.

4. 4

   Repair wiring harness

   If the diagnostic checks revealed damaged wiring, repair or splice the affected section of the harness using proper weather-sealed connectors.

5. 5

   Remove faulty switch

   If the switch itself is faulty, depress the retaining tabs on the sides of the rocker switch and push it out of the console panel.

6. 6

   Install new switch

   Snap the new OEM climate control switch into the panel until it clicks securely into place.

7. 7

   Reconnect switch

   Reconnect the electrical connector to the new switch.

8. 8

   Reassemble console

   Reinstall the console trim panels.

9. 9

   Test and clear codes

   Reconnect the battery, turn the ignition on, and use a diagnostic tool or the AFS Pro display to clear the fault code. Test the climate control system to verify the temperature decrease function operates correctly.