HVACopediaGoodman · Heat pump
A2 Outdoor air temperature sensor fault
What the control is telling you
The outdoor control reads the outdoor air temperature (OAT) sensor as open, shorted, unplugged or out of its normal range. The OAT reading is used for balance point and dual fuel decisions.
Applies to: ComfortNet heat pumps ASZC/GSZC/DSZC (PCBHR104/105 outdoor control)
Likely causes
- Sensor unplugged or loose at the outdoor control
- Open or shorted sensor or sensor leads
- Sensor value outside the valid range
Test and repair steps
- Warning: Kill power to the outdoor unit before touching wiring, the compressor terminals or the control.
- Check that the OAT sensor plug is fully seated on the outdoor (UC) control and the leads are not pinched or chafed.
- Unplug the sensor and measure it with an ohmmeter: about 10,000 ohms (plus or minus 10%) near 75-77 F. Compare other temperatures with the sensor resistance chart (Specs tab).
- Replace the sensor if it reads open, shorted or far off the chart, then restore power and confirm the code clears.
Models that show this code
24 models in Goodman/Amana ComfortNet ASZC/GSZC/DSZC
Other codes on the same units
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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; sensor check p.42-43. 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.