11/13/25
Message Overview:
| DDG Reference: | 30-31-02 |
| Pilot Action (QRH): | ADVISORY 10-4 |
| System Description: | 30-31-00 - Air Data Probes and Sensors |
| Schematic Diagram: | [ Global Express ] [ G5000 ] [ Global XRS ] - 30-31-00-101 - Air Data Sensor Heat Control System |
| Wiring Diagram: | [ Global Express ] [ G5000 ] [Global XRS ] - 30-31-00-01 - Heat Control System (Left) - ALL |
Message Description:
The HBMU1 is not serviceable because of a fault condition.
Possible Causes:
- Interface wiring between Cockpit Circuit Breaker Panel (CCBP) and Heater/Brake-Temperature Monitoring Unit (HBMU)
- Heater/Brake-Temperature Monitoring Unit (HBMU) 1
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None
Flight Operation Notifications Manual (FONM):
- [ Global Express ] [ G5000 ] [ Global XRS ] FON 01-16 ICE-002, [PITOT 1 (2) (3) HT FAIL] (Caution/Amber), [L (R) AOA HEAT FAIL] (Caution/Amber), [STBY PITOT HT] (Caution/Amber), [ICE DETECTOR FAULT] (Advisory/Cyan), [L (R) PROBE MON FAIL] (Advisory/Cyan) or [TAT HT 1 (2) (3) FAIL] (Advisory/Cyan) On Ground.
Quick Links:
| Standard Aircraft Configuration for Maintenance | [ G5000 ] [ Global Express ] [ Global XRS ] AMM12-00-00-867-801 |
| Connect Electrical Power to the Aircraft | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-00-00-861-801 |
| Electrical/Electronic Safety Precautions | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-00-00-910-801 |
| Electrostatic Discharge Safety Precautions | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-00-00-910-802 |
| Removal of the Heater/Brake-Temperature Monitoring Unit (HBMU) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM30-31-01-000-801 |
| Installation of the Heater/Brake-Temperature Monitoring Unit (HBMU) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM30-31-01-400-801 |
| Access to Active Faults | [ G5000 ] [ Global Express ] [ Global XRS ] AMM45-45-00-970-802 |
| Access to Stored Faults | [ G5000 ] [ Global Express ] [ Global XRS ] AMM45-45-00-970-803 |
| Access to System Diagnostics | [ G5000 ] [ Global Express ] [ Global XRS ] AMM45-45-00-970-804 |
Troubleshooting Recommendations:
- Using the PMAT, access the Active Faults/Stored Faults as per AMM Tasks.
- Select related CAIMS message below:
- Measure for 115 VAC inputs to HBMU1.
From To Expected Result Result HBMU 1 - A121P1-L Ground 115V AC HBMU 1 - A121P1-H Ground 115V AC HBMU 1 - A121P1-B Ground 115V AC HBMU 1 - A121P1-E Ground 115V AC HBMU 1 - A121P1-A Ground 115V AC HBMU 1 - A121P1-N Ground 115V AC - Are the results good?
- If all 115 VAC inputs present, go to step 7.
- If any of the 115 VAC inputs is missing, continue with next step.
- Perform wiring checks between HBMU1 and Cockpit Circuit Breaker Panel (CCBP).
From To Expected Result Result HBMU 1 - A121P1-L CCBP -A35P/J3-D Continuity HBMU 1 - A121P1-H CCBP -A35P/J3-F Continuity HBMU 1 - A121P1-B CCBP -A35P/J3-L Continuity HBMU 1 - A121P1-E CCBP -A35P/J3-M Continuity HBMU 1 - A121P1-A CCBP -A35P/J2-D Continuity HBMU 1 - A121P1-N CCBP -A35P/J6-B Continuity - Are the results good?
- If YES, continue with next step
- If NO, repair as required and do close out.
- Measure for 28 VDC inputs to HBMU 1
From To Expected Result Result HBMU 1 - A121P2-1 Ground 28V DC - Are the results good?
- If YES, go to step 12.
- If NO, continue with the next step.
- Perform wiring check between HBMU 1 and SPDA 2.
From To Expected Result Result HBMU 1 - A121P2-1 SPDA 2- A14P1-G Continuity - Are the results good?
- If YES, continue with next step.
- If NO, repair as required and do close out
- Interchange the SPDA 2, does system check good?
- If YES, do the close out.
- If NO continue with next step.
- Interchange HBMUs replace defective unit.
- Do close out.