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Error code reference

Goodman Heat Pump Error Code A2

Outdoor air temperature sensor fault

Goodman codesGoodman heat pump codes

Outdoor air temperature sensor fault - shorted, open, disconnected, or out of range sensor.

First step from the service manual

Check sensor connection. Replace open/shorted sensor.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
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What A2 means on a Goodman heat pump

The A2 error code on a Goodman heat pump indicates a fault with the outdoor air temperature (OAT) sensor. This sensor is a thermistor, a resistive device whose electrical resistance changes predictably with temperature. The control board continuously monitors the resistance signal from this sensor to determine outdoor ambient conditions, which directly influences defrost cycle timing, supplemental heat lockout, and other temperature-dependent operating parameters. When the board detects a signal that falls outside the expected resistance range, or receives no signal at all, it triggers the A2 fault.

The fault can result from three primary electrical conditions: a short circuit (where the sensor resistance reads abnormally low, indicating the circuit is collapsed), an open circuit (where resistance is effectively infinite, meaning the signal wire is broken or disconnected), or an out-of-range reading that does not correspond to any valid temperature within the sensor's calibrated operating window. Each of these conditions prevents the control board from making accurate decisions about system operation.

Physically, the outdoor air temperature sensor is typically mounted on the outdoor unit and exposed to environmental conditions including moisture, UV exposure, and temperature extremes. These conditions can degrade the sensor body, connector pins, or wiring harness over time. Rodent damage to wiring is also a common field finding. The first diagnostic step is to inspect the sensor connector at the control board and at the sensor itself, checking for corrosion, bent pins, or visible wire damage before condemning the sensor itself.

Source: manufacturer service documentation.

Common causes of A2

  1. 01

    Loose or disconnected sensor connector

    Wiring / connection

    The sensor connector at the control board or at the sensor itself may have vibrated loose or pulled free. Inspect both ends of the wiring harness for a secure, fully seated connection.

  2. 02

    Failed outdoor air temperature sensor

    Part replacement

    The thermistor element inside the sensor can fail open or short over time due to age, moisture intrusion, or thermal cycling. A multimeter resistance check across the sensor terminals will confirm an open or shorted reading outside the normal range.

  3. 03

    Corroded or damaged connector pins

    Wiring / connection

    Exposure to outdoor moisture can corrode the sensor connector pins, increasing resistance in the circuit or breaking the signal entirely. Look for green or white oxidation at the connector and clean or replace as needed.

  4. 04

    Damaged wiring harness

    Part replacement

    The sensor wire run from the outdoor unit can be damaged by rodent chewing, pinching during panel installation, or UV degradation. Inspect the full length of the sensor wire for cuts, abrasion, or breaks.

  5. 05

    Extreme ambient temperature condition

    Wiring / connection

    If actual outdoor temperatures fall outside the sensor's rated measurement range, the control board may log an out-of-range fault even with a functional sensor. Verify that current ambient conditions are within normal operating parameters before replacing components.

See the test procedure for each cause

Frequently asked questions about A2

What does A2 mean on a Goodman heat_pump?
The A2 code indicates a fault with the outdoor air temperature sensor. The control board has detected that the sensor signal is shorted, open, disconnected, or outside the valid measurement range. This sensor is critical for defrost control and other temperature-dependent functions. The system flags this fault to prevent operating on inaccurate data.
Can I fix the A2 error code on my Goodman heat pump myself?
A homeowner with basic electrical knowledge can safely inspect the sensor connector for visible damage, corrosion, or a loose connection without any risk. However, accurately testing the sensor with a multimeter and tracing wiring faults through the outdoor unit typically requires familiarity with low-voltage control circuits. If the sensor itself needs replacement, a technician can source the correct part and ensure proper calibration with the control board.
Is it safe to run my Goodman heat pump with an A2 fault active?
Operating the system with an A2 fault is not recommended for extended periods. Without a valid outdoor temperature reading, the control board cannot properly manage defrost cycles or supplemental heat lockout, which can lead to reduced efficiency, ice buildup on the outdoor coil, or excessive auxiliary heat use. Address the fault promptly to avoid potential secondary damage.
Will resetting the heat pump clear the A2 error code?
A power reset may temporarily clear the A2 code from the display, but if the underlying sensor fault still exists, the code will return once the control board re-checks the sensor signal. A reset is useful for confirming whether the fault is intermittent, but it is not a repair. The sensor connection and sensor condition must be addressed to resolve the fault permanently.
How much does it cost to repair a Goodman heat pump A2 sensor fault?
If the issue is simply a loose connector, the repair cost may be limited to a service call fee, typically in the range of $75 to $150. If the outdoor air temperature sensor requires replacement, parts and labor combined generally fall in the range of $100 to $300 depending on the specific model and local labor rates. Wiring harness repairs can vary more widely depending on the extent of the damage.

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