HVACopediaNTI · Boiler
03 09 Gas relay check failed
What the control is telling you
The gas relay check on the PCB failed.
Applies to: TRX150
Likely causes
- Internal PCB fault
- Gas valve or relay fault
Test and repair steps
- Switch the boiler off and back on at the main electrical supply.
- If the problem returns, replace the main PCB.
Models that show this code
5 models in TRX
Other codes on the same units
- 03 04 Too many resets in 15 minutes (more than 5)
- 03 05 PCB internal error
- 03 06 PCB internal error
- 03 07 PCB internal error
- 3 P9 Scheduled maintenance: call for service
- 4 11 Room sensor open or short circuit, Zone 1
- 4 12 Room sensor open or short circuit, Zone 2
- 4 13 Room sensor open or short circuit, Zone 3
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Source: NTI TRX150 manual, p. 91. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.