HVACopediaGoodman · Heat pump
b9 Indoor airflow lower than requested
What the control is telling you
The indoor unit reports it is delivering less airflow than the outdoor unit asked for. The system may run at reduced capacity or stay on low stage when high stage is expected.
Applies to: Communicating 2-stage condensers and heat pumps with the PCBHR104 or PCBHR105 outdoor control (7-segment display): ASXC16/18, GSXC16/18, DSXC16/18, ASZC16/18, GSZC16/18, DSZC16/18
Likely causes
- Indoor blower motor problem
- Dirty or blocked filters
- Undersized or restrictive ductwork
- Indoor and outdoor units not an approved match
Test and repair steps
- Inspect and replace filters; check the coil, return grilles and supply registers for blockage.
- Measure total external static pressure and compare with the indoor unit's spec sheet limit; correct duct restrictions or resize as needed.
- Check the indoor blower motor operation.
- Confirm from the spec sheets that the indoor and outdoor models are an approved match.
Models that show this code
24 models in Goodman/Amana ComfortNet ASZC/GSZC/DSZC
Other codes on the same units
- 09 Low 24 V control voltage
- A2 Outdoor air temperature sensor fault
- A3 Outdoor coil temperature sensor fault
- b0 Indoor blower not running when it should be
- d0 No shared data on the network
- d1 Invalid shared data on the network
- d2 System mismatch - indoor unit cannot supply required airflow
- d3 Configuration mismatch - shared data does not match hardware
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Source: Goodman ComfortNet ASXC/GSXC/DSXC, ASZC/GSZC/DSZC, AVPTC/MBVC service manual, Unitary Diagnostic Codes PCBHR104 p.71-77 and PCBHR105 p.78-84. 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.