Case IH F-3509-4 - CGR – CGR: Sensor Supply Voltage 1: Voltage Below Normal

The supply voltage powering the receiver (or its internal 5V reference circuit) has dropped below the acceptable operating threshold. This condition is typically caused by a short circuit to ground, a damaged wiring harness, severe moisture intrusion, or an internal failure within the receiver itself.

• MAGNUM AFS Connect
• STEIGER AFS Connect
• Case IH AFS Connect Magnum Tractors (Models 180, 200, 220, 240, 250, 280, 310, 340, 380)
• Case IH Steiger / Quadtrac series with AFS Connect

1. 1

   Verify that the machine's battery and alternator are outputting the correct system voltage, as low overall machine voltage can trigger supply faults.

2. 2

   Visually inspect the CGR serial interface cable and the cab roof wiring harness for physical damage, chafing, pinched wires, or rodent damage.

3. 3

   Disconnect the harness at the CGR receiver and inspect the connector for moisture ingress, corrosion, bent pins, or pushed-back terminals.

4. 4

   With the key ON and the receiver disconnected, use a multimeter to measure the supply voltage pin at the harness connector to verify correct voltage from the cab controller.

5. 5

   Test the supply wire for continuity to ground to rule out a short in the harness.

1. 1

   Power down the tractor and turn off the main battery disconnect switch.

2. 2

   Safely access the roof of the cab to reach the CGR receiver.

3. 3

   Disconnect the CGR serial interface cable from the back of the receiver.

4. 4

   If your diagnostic tests revealed a short to ground in the wiring, trace the harness back into the cab roof and repair the damaged wire, or replace the CGR serial interface cable entirely.

5. 5

   If the wiring harness tests perfectly (proper voltage is present and there are no shorts), the fault is an internal hardware short within the CGR receiver's power supply.

6. 6

   Unbolt the mounting bracket hardware and remove the faulty CGR receiver.

7. 7

   Install the replacement CGR receiver and secure it to the mounting bracket.

8. 8

   Reconnect the serial interface cable, ensuring the connector is fully seated and locked to prevent moisture entry.

9. 9

   Turn on the battery disconnect and turn the ignition key to the ON position.

10. 10

    Boot up the AFS Pro display and verify that the F-3509-4 fault code is now inactive and that the GNSS receiver successfully acquires a satellite signal.