23-NA-221

Subject: A/C Inoperative and/or Only Blows Warm Air Due to Faulty Solar Sensor
Brand:
Model
Year:
Model:
from
Buick
VIN Breakpoint:
to
from
to
2024
—
—
Engine:
Transmission:
—
—
Electra E5 2024
Cadillac
LYRIQ
2023
Blazer EV
Chevrolet
Equinox
EV
2024
Involved Region or Country
North America, Europe, China, Korea
Condition
Some customers may comment that their A/C system is inoperative and/or only blows warm to hot
air.
Cause
The condition may be caused by an internal circuit fault within the upward-facing light (solar) sensor.
This circuit fault provides a high voltage signal consistent with an extremely low cabin air/surface
temperature reading and this causes HVAC system to respond by delivering full heat.
Correction
Replacement of the solar sensor on vehicles with sensors that display voltages in scan tool outside
normal operating parameters (>4.5V).
Service Procedure
Important: This technical service bulletin (TSB) can only be completed by certified repair facilities who have met all
specific training, tool and equipment requirements pertaining to the vehicle Brand and Model serviced. Repairs must be
performed by a technician who has successfully completed the required training.
Important: Service agents must comply with all International, Federal, State, Provincial, and/or Local laws
applicable to the activities it performs under this bulletin, including but not limited to handling, deploying,
preparing, classifying, packaging, marking, labeling, and shipping dangerous goods. In the event of a conflict
between the procedures set forth in this bulletin and the laws that apply to your dealership, you must follow
those applicable laws.
Note: Conduct this procedure PRIOR to performing standard A/C diagnostics methods, including checking system
pressures.
1. Place the vehicle in Service Mode.
2. Connect the scan tool and navigate to the Passenger Compartment Air Temperature Sensor voltage value, using
the following path: Module Diagnostics, [K9] Body Control Module, Data Display, HVAC Sensor Data.
3. Verify Passenger Compartment Air Temperature Sensor voltage reading is <4.5V, and the Left Front Passenger
Compartment Air Temperature reading is within +/-10°C (50°F) of current shop temperature.
3.1. If the voltage reading is >4.5V, it is necessary to replace the sensor.
3.2. If the voltage reading is <4.5V, the sensor is operating correctly. Continue with the standard HVAC diagnostics
in SI.
Parts Information
* We believe this source and their products to be reliable. There may be additional manufacturers of such
products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the
products or material from this firm or for any such items that may be available from other sources.
Causal
Part
Description
Part Number
Qy
t
X
SENSOR, SUN LOAD & AMB LGT & CHRG IND
84847757
1
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation
4420370
Description
Labor Time
Sun Load, Ambient Light, and Charge Indicator Sensor Replacement Use Published Labor Operation Time
Version
1
Modified
Released December 15,
2023