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B2AF614

DTC B2AF614 indicates a power supply circuit fault for the Rear HVAC Blower Motor, specifically a short to ground or an open circuit — Atto 3

Thermal Management System

DTC B2AF614 indicates a power supply circuit fault for the Rear HVAC Blower Motor, specifically a short to ground or an open circuit.

This fault affects the rear air delivery function of the HVAC system, part of the thermal management subsystem.

A short to ground typically indicates damaged blower motor power harness insulation contacting the vehicle body ground, or failed internal motor winding insulation.

An open circuit indicates a break in the circuit resulting from a severed wiring harness, a loose connector, or internal motor burnout.

This fault completely disables the rear HVAC blower function and impairs cabin temperature regulation.

This classifies as a severe fault because short-circuit currents can overheat the wiring harness or blow a fuse in extreme cases.

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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1Prolonged overload operation or motor aging typically burns the internal winding or damages the insulation of the rear blower motor, causing a short to ground.
  • 2Chafing, crushing, or water ingress damages the wiring harness insulation under the vehicle floor or seats, causing a short to ground against the metal body.
  • 3Internal power drive circuit fault in the rear air conditioning control module (Rear HVAC ECU); fails to output the PWM control signal or provide power.
  • 4Blown blower power supply fuse or burnt relay contacts causing an open circuit (usually a secondary fault).
  • 5Water ingress, oxidation, or loose pins at the rear seat area wiring harness connector (usually located at the rear of the centre tunnel or below the C-pillar) causing poor contact or an open circuit.
What To Do
  • 1
    Use the BYD VDS diagnostic tool to read the complete fault code stream, confirm B2AF614 is a current (Active) fault rather than a history fault, and check for related communication fault codes.
  • 2
    Disconnect the 12V battery negative terminal and wait 3 minutes. Remove the rear seat and the centre tunnel rear trim panel to expose the rear blower assembly (usually located on the front wall of the boot or beneath the rear seat).
  • 3
    Measure the resistance between the two blower motor pins. The normal value is 2-5 Ω (12V system) or 1-3 Ω (high-voltage platform after DC-DC step-down). A resistance of 0 Ω indicates an internal short circuit; infinite resistance indicates an open circuit.
  • 4
    Disconnect the blower motor connector and use a multimeter to measure the resistance between the harness-side power supply terminal and ground: if the resistance is less than 1 Ω, a short to ground exists; inspect the wiring harness routing for wear points. If the resistance is infinite, an open circuit exists; check fuse EF11/EF12 (depending on vehicle model) and the relay.
  • 5
    Check the power supply (B+), ground (GND), and PWM signal wires of the blower control module (if equipped as an independent module). Use an oscilloscope to verify the PWM waveform is normal (typically a 1kHz-10kHz duty cycle signal).
  • 6
    If the wiring harness is normal, replace the rear blower assembly (part number varies by vehicle model, e.g., RA-8121200). If the wiring harness is damaged, repair it with heat-shrink tubing and re-secure the harness to prevent rubbing against the vehicle body.
  • 7
    Reconnect all connections, clear the fault code, start the vehicle, and test all rear air conditioning fan speed settings. Use the diagnostic tool to read the data stream and confirm the blower feedback current is within the normal range (usually 2-15A).
Real-World Cases
BYD DTC AI Analysis

Song MAX rear blower motor wiring harness chafed and shorted to ground

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Vehicle: 2018 Song MAX DM, 62,000 km. Symptoms: Dashboard intermittently displayed "AC System Fault" when the rear air conditioning was switched on; rear vents stopped blowing while the front remained normal. Diagnosis: Scanned DTC B2AF614 (current fault). Measured blower motor resistance at 0.8 Ω (abnormally low). Disassembly revealed the rear blower motor power harness grommet had dislodged at the floor pan sheet metal hole; the sharp edge cut through the insulation, shorting to ground. Repair: Cut and reconnected the damaged harness with heat-shrink tubing, reinstalled the rubber grommet and wrapped with cloth tape, replaced the blower fuse (15 A). Fault resolved.
BYD DTC AI Analysis

Water ingress caused corrosion in the rear blower motor connector on the Qin EV.

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Vehicle: 2019 BYD Qin EV High Range. Fault: Rear air conditioning inoperative after heavy rain, front system normal. DTC B2AF614 present; measured 0V at blower supply. Inspected wiring harness connector beneath rear seat and found water ingress and copper oxide causing open circuit. Cause: Water entered through seat rail seals during wading; connector waterproof seal aged and failed. Fix: Cleaned contacts with electronic cleaner, blow-dried with air gun, applied conductive grease, replaced waterproof seal. Resolved.
BYD DTC AI Analysis

Rear blower motor burnout and replacement case

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Vehicle: 2019 BYD Song MAX gasoline. Symptoms: Burning smell when rear AC turned on, followed by complete loss of airflow. Scanned DTC B2AF614. Tear-down found blower motor brushes severely worn and commutator burnt, causing internal short. Resistance between motor terminal and housing measured 0.2Ω (severe short to ground). Cause: Long-term operation in dusty conditions without regular cabin filter replacement caused excessive blower load. Repair: Replaced rear blower assembly (including fan impeller), thoroughly cleaned AC ducts, replaced cabin filter. Issue resolved.
BYD DTC AI Analysis

AC control module driver fault false positive

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Vehicle: 2017 Song MAX. Symptom: Rear air conditioning operates intermittently; DTC B2AF614 present intermittently. Initial inspection showed normal wiring harness and blower motor resistance. Further diagnosis found a dry solder joint on the rear blower MOSFET driver chip inside the AC control module (AC ECU), causing an intermittent open circuit. The module failed to maintain stable voltage output to the blower. Solution: Replaced the AC control module (after programming and matching). Fault eliminated. When diagnosing intermittent faults, verify control module output stability.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.