Roewe Plug-in Hybrid A/C System Circuit Repair Guide (Low-Spec ATC)

Fault Background

The low-spec ATC (A/C control head - low spec) circuit of the Roewe plug-in hybrid (manual 847, S24~S29 A/C system circuits) groups six functional families on the same control head: blower speed control (PWM module), temperature/sun sensor family, air quality purification family (AQS + PM2.5 + negative ion), dual expansion valves (cabin TXV / battery chiller TXV), electric A/C compressor (LIN), rear window defogger (CR5 relay). Power is supplied from KL15/KL30/KL58, distributed hierarchically through the engine compartment and passenger compartment fuse boxes; the control head itself routes all signals through connectors such as FA043/FA060. This article organizes repair points by circuit page.

Power Supply and Fuse Distribution

Hierarchical power supply: Engine compartment fuse box (CB001 main busbar) → Passenger compartment fuse box (CF22 busbar) → Each branch fuse. The blower high-current branch is independently powered by F52 56A; the control head IGN terminal is powered via KL15/KL15 SW through the passenger compartment fuse box; the rear window heater is controlled output from KL30 battery power via CR5 relay; background lighting uses KL58.

Repair points: If the blower does not run, first check F52 (56A) and voltage drop across busbars CB001/CF22; if the control head is completely dead, first check the KL15 SW branch fuse and ground; if the defogger is not heating, check the KL30 branch and CR5 contacts, rather than suspecting the heating element directly.

Blower Speed Control Circuit

Structure: A/C control head → Blower Ctrl PWM1 command line → Blower speed control module (Blower F/B1+ / F/B1- power supply, KL31 ground) → Module outputs PWM to drive the blower motor. The control head interconnects with the module via connectors such as FA051/FA060/FA043.

Repair points: If module power is normal but the blower has no airflow → measure the PWM1 command line (use an oscilloscope to check duty cycle; 0% or floating indicates missing command); if the command is normal, the module heats up but the motor does not move → check voltage drop on the F/B1+/- lines to the motor and the motor itself; if the module has no output, it is mostly an internal power transistor failure; after replacement, recheck ground KL31.

Temperature and Sun Sensor Family

In-vehicle temperature sensor (ITOS): Integrated NTC and sun sensor, four wires—ITOS_NTC_REF (reference), ITOS_SUN (sun), GND_ITOS (ground), ITOS_NTC (temperature signal), connected to the control head via FA043.

Vent/evaporator/ambient sensors: Footwell vent temperature sensor (Foot Temp. Sensor1), left face vent temperature sensor (Face Temp. Sensor1), evaporator temperature sensor (Evap. Temp. Sensor), ambient temperature sensor (Ambient Temp. Sensor)—all three-wire 5V/Signal/GND; left and right sun sensors (Solar Sensor_L/R).

Fresh/recirculation air motor: Reci./Fresh Flap Motor+/- dual-wire drive, control head controls the recirculation flap via FA015.

Repair points: If multiple sensors report faults simultaneously, first check 5V reference and common ground (one open circuit can pull down the entire group reading); if a single reading is abnormal (e.g., ambient temperature constantly -40°C), prioritize checking that sensor's connector and wiring for short to ground; if the recirculation flap does not move, check the motor's forward/reverse line continuity and binding, rather than replacing the motor first.

Air Quality Purification Family

Three independent circuits share the control head: Air quality sensor AQS (connected via FA140, detects outside exhaust and automatically switches to recirculation), PM2.5 sensor (FA107, PM2.5 Enable + Feedback dual lines), negative ion generator (FA028, PWR supply + Ion Generator Driver + GND). All three are powered from the control head side via their respective fuses/grounds (EB084/BY118, etc.).

Repair points: If the purification family fails entirely, first check the control head side enable output; if PM2.5 has enable but no feedback → check the sensor itself or the feedback line for open; if the negative ion generator has a "hissing" sound on the high-voltage side but no effect → check the ion emitter head for dust accumulation and high-voltage wire insulation.

Dual Expansion Valves and Compressor Circuit

Dual expansion valves: Cabin TXV and Chiller TXV are both solenoid-operated expansion valves, with PWR supply + GND ground (EB084/BY118 lines), controlled by the control head based on cooling load and battery thermal management requests.

Electric A/C compressor (low spec): The A/C control head - low spec sends speed commands to the compressor via LIN single wire (EB070/EM121A/FA151 link); compressor power is dual KL30_Hybrid and KL30, grounds KL31_Hybrid and KL31; the control head connects to the vehicle CAN (CANH/CANL) to obtain vehicle status.

Repair points: Poor cooling but compressor does not start → first check the LIN link (open/short to ground) and compressor power; compressor frequently trips → check dual TXV solenoid valve sticking causing low-pressure protection; compressor abnormal noise/vibration → after power-off, check insulation and three-phase (only after high-voltage discipline is followed).

Rear Window Defogger Circuit

Control link: A/C control head → Defog Relay Drive → CR5 window/mirror heating relay (R5-30 contact / R5-85 coil) → rear window heating element (Heated Rear Window); F55B/F63A/F63B provide staged protection, status is displayed on the center screen. Defogging automatically exits according to a timed strategy; if it does not exit when held, it is mostly relay contact sticking.

Key Parameter Quick Reference

Safety Warnings

• This article is for technical reference. A/C system repair must be performed by professional technicians per OEM specifications. When involving high-voltage compressor/battery cooling circuits, follow vehicle high-voltage discipline (training threshold / disconnect 12V / remove MSD / insulated gloves leak check / wait 5 min).
• The electric A/C compressor is a high-voltage component: personnel not trained on this vehicle's high-voltage system are strictly prohibited from disassembling; verify voltage before measuring, range must be greater than 400V.
• Blower F52 is a 56A high-current branch: live plugging/unplugging of the speed module connector may cause arcing and damage terminals; always power off before operation.
• Refrigerant circuit (TXV/compressor) repair requires refrigerant recovery first; do not open lines to vent directly.

Repair Insights

The most valuable lesson from this wiring diagram is "low spec does not mean simple": one A/C control head - low spec simultaneously handles blower PWM, seven temperature sensors, three purification devices, dual TXVs, LIN compressor, and defogger relay; any one short to ground can black out the entire control head. For repair sequence, first check hierarchical power supply (F52/CB001/CF22 busbar voltage drop) → then check common references (5V and ground) → finally check individual branches, which avoids many unnecessary part replacements. Two details to remember: defogger relay CR5 is a battery-powered circuit, still live after key removal, treat it as battery power when checking; compressor uses LIN rather than hardwired, the old method of "measuring speed signal line voltage" does not apply to this vehicle—LIN is digital messages, must use oscilloscope or diagnostic scan tool to view waveform/read status. Finally, ground discipline: blower module KL31, compressor KL31_Hybrid and KL31 dual grounds, sensor common GND—poor ground connections in this circuit often manifest as "multiple unrelated faults appearing simultaneously."

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【This article is for reference only】