Garmin GRA 55 Maintenance Manual - Page 27

5 TROUBLESHOOTING INFORMATION 5.1 GRA 55/5500 General Troubleshooting This section provides troubleshooting information for the Garmin GRA 55/5500 Radar Altimeter. All faulty units must be returned to Garmin for repair. No internal or comprehensive unit troubleshooting is possible at the dealer service center due to the need for specialized unit test setups and test software. However, the service center may troubleshoot a unit to confirm a fault or the status of the unit by utilizing the following methods: • Checking the status of monitored unit faults • Checking the unit software versions • Checking the unit installation configuration • Downloading and analyzing the unit assert log • Checking the unit statistics and internal recorded unit temperatures The troubleshooting methods listed herein are employed using the GRA 55/5500 Retrofit Installation Tool as described in the following sections. Table 5-1. GRA 5500 Fault Descriptions Fault Type Fault Name Configuration N/A Zero-Foot Lock Calibration Zero-Foot Cal Description Cause Resolution GRA HW Revision Update software to ID invalid for SW correct version for version hardware Unit does not boot GRA Unit ID invalid (Both discrete inputs grounded) Check Unit ID strapping and set to a valid ID Hardware failure Return unit to Garmin for service Average frequency of zero-foot signal is larger/smaller than allowable frequencies Improper antenna connections Check antenna installation and all cable connections and retry calibration. Note there are no assert log entries for this fault. Zero-Foot point is Calibration not not set complete Calibrate unit while on ground. Note there are no assert log entries for this fault. 190-01277-A3 Rev. 1 System Maintenance Manual GRA 55/5500 Bell 206 STC Page 5-1