What It Means
Defrost Fault B or C detected on the outdoor unit.
Trane AC & Heat Pump
Trane AC & Heat Pump Error Code Red 3 Flashes
Troubleshooting guide for the Trane AC & Heat Pump system fault Red 3 Flashes.
Possible Causes
- Non-functioning outdoor fan in heat mode.
- Excessive outdoor coil icing.
- Faulty defrost or ambient temperature sensor.
- Defective control module.
Not sure which one it is — or if it's none of these? Try ACLogics today.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis
Defrost Fault B (and/or C).
All Recorded Causes
Verify the outdoor fan is running during heat mode and check for icing. If red 3 blinks continue, have a technician check the defrost sensor, ambient sensor, and control module.
Verify Before Replacing Parts
- Confirm the exact Trane model family and ac and heat pump context before acting on a generic code description.
- Verify the sensor or thermistor reading against the expected range for the current operating condition, keeping in mind that verify the outdoor fan is running during heat mode and check for icing.
- Check the sensor harness and board connection before condemning the sensor itself; on Trane units this is also where you'd confirm if red 3 blinks continue, have a technician check the defrost sensor, ambient sensor, and….
- After the correction, run the system long enough to confirm the ac and heat pump fault does not return under normal load.
Not sure which system this Trane code is on?
ACLogics has guided diagnostics for 36 Trane fault codes and asks the right questions to narrow it down.
