Case IH 518854-04 - VCM – VCM: 12VR supply voltage low

The control module is detecting that the voltage at the 12VR power input/supply rail has dropped below the normal operating threshold.

• MAGNUM AFS Connect
• Planters

1. 1

   Verify the voltage level on the main power (PWR) supply coming from the tractor to the module to ensure system voltage is not below normal

2. 2

   Inspect the power (PWR) control relay located in the VCM/UCM enclosure to determine if it has failed to operate

3. 3

   Inspect the power fuses (specifically PWR fuse 3 in module enclosures) to see if the circuit is open or blown

1. 1

   Measure Supply Voltage

   Use a multimeter to measure the main power voltage reaching the VCM. If the voltage is low at the source, troubleshoot the tractor's main battery, alternator, and primary battery cables.

2. 2

   Test/Replace the Power Relay

   Locate the power control relay for the VCM. Test the relay for proper continuity and switching. Replace the relay if it fails to operate.

3. 3

   Inspect and Replace Fuses

   Check the fuses in the VCM enclosure (e.g., Fuse 3). If a fuse is open, check the circuit for shorts to ground, then replace the fuse with one of the exact same amperage.

4. 4

   Harness & Module Check

   If the main power, relay, and fuses are all functioning correctly, inspect the wiring harness for damage that could be drawing the 12VR voltage down. If the harness is intact, the VCM itself may have an internal fault requiring replacement.