Case IH F-7820-5 - CGR – CGR (Common GNSS Receiver): GPS / GNSS Antenna Circuit Open or Current Below Normal

The control module is detecting an open electrical circuit or abnormally low current draw on the GNSS antenna circuit. This means the receiver cannot detect the physical connection to the antenna, which results in a loss of satellite positioning data.

• MAGNUM AFS Connect
• STEIGER AFS Connect
• Case IH AFS Connect Magnum Tractors (180, 200, 220, 240, 250, 280, 310, 340, 380)
• Case IH combines (e.g., 2388)
• Case IH sprayers

1. 1

   Visually inspect the physical connection between the GNSS antenna and the CGR module, ensuring TNC/SMA connectors are tight and free of corrosion or moisture.

2. 2

   Perform a cable continuity test using a Digital Multimeter (DMM) on the coaxial antenna cable from end to end to rule out a severed wire.

3. 3

   Test the antenna cable for a short to ground to rule out wire chafing.

4. 4

   Verify that the power supply to the transceiver/module is within the allowable operating range (10.8VDC to 31.2VDC).

1. 1

   Power Down

   Turn off the machine and disconnect battery power to prevent electrical spikes to the AFS display or CGR module.

2. 2

   Isolate the Fault

   Disconnect the GNSS antenna cable from both the roof-mounted antenna and the CGR module.

3. 3

   Test/Replace the Cable

   If the DMM continuity test reveals an open circuit in the cable, replace the antenna cable harness. Route the new cable carefully to avoid pinch points in the cab roof structure.

4. 4

   Test/Replace the Antenna

   If the cable tests good, the internal circuitry of the GNSS antenna itself has failed open. Unbolt the faulty GNSS antenna from the mounting bracket and install the replacement unit.

5. 5

   Reassemble and Clear Codes

   Reconnect all TNC fittings securely. Restore battery power, boot up the AFS display, and verify that the GNSS signal strength graph shows satellite acquisition. Use the Electronic Service Tool (EST) to clear the F-7820-5 inactive fault code.