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Definition only
B0278: HVAC Defrost Door Circuit
Standardized SAE J2012 code · B02xx codes
What does B0278 mean?
A fault is detected in the HVAC defrost door actuator circuit; defrost airflow may not engage.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Warning light or symbol related to the affected system
- Comfort or safety function impaired
Common causes
- High Defrost actuator failed
Likelihood is a general estimate across vehicles; your make and model may differ.
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