Description
Sensor for Solar Radiation Intensity for Citroën and Peugeot Vehicles
The Sunlight Intensity Sensor 643604 is a direct-fit electrical component designed for Citroën and Peugeot models with automatic climate control. It detects incoming solar radiation and provides the HVAC control unit with real-time data so the air-conditioning and blower adapt to changing sunlight conditions. Commonly searched under part numbers 643604, 105182352 B, 105487416 B and A66100100, this sensor is suitable for professional workshops and DIY mechanics looking for a reliable replacement part.
Technical Information
- Manufacturer: Stellantis (Citroën / Peugeot OEM)
- Model: Citroën C4 Picasso; Citroën C8; Peugeot 807
- Product Codes: 643604
- Additional Numbers: 105182352 B, 105487416 B, A66100100
Function
The sensor measures the intensity and angle of sunlight falling on the vehicle. The climate control unit uses this information to adjust blower speed, air distribution and air conditioning load to maintain passenger comfort and reduce cabin overheating. Accurate solar detection improves automatic temperature regulation and reduces unnecessary A/C cycles, helping with fuel economy and occupant comfort.
Fitment And Replacement
Location: Usually mounted on the dashboard near the base of the windshield or behind an upper-dashboard cover in the centre of the vehicle. Access varies by model—some vehicles require removal of small trim pieces or the upper dash cover.
Replacement Steps (typical):
- Remove the dashboard trim or cover that conceals the sensor. Use plastic trim tools to avoid damaging panels.
- Unplug the electrical connector from the sensor. Inspect connector and wiring for corrosion or damage.
- Remove the sensor from its mounting (clips or small screws are common) and install the new unit in the same orientation.
- Reconnect the electrical connector and reassemble trim. Ensure the sensor lens is clean and unobstructed by trim or adhesives.
- Start the vehicle and verify that the climate control responds to sunlight changes (a flashlight can simulate sun for a quick check).
Installation Recommendations
- Handle the sensor lens carefully to avoid scratches or contamination—fingerprints and adhesive residue can affect readings.
- Ensure connector pins are clean and fully seated. Replace or repair any damaged wiring or corroded terminals before final assembly.
- After installation, verify proper HVAC behavior by testing in varying light conditions. If the vehicle shows fault codes related to the sensor, diagnose via an appropriate diagnostic tool.
- Use manufacturer-recommended trim tools and follow vehicle-specific disassembly procedures to avoid damaging clips or the dashboard surface.
Most Common Failure Reasons
- Water ingress or humidity causing corrosion or electrical faults at the connector.
- Physical damage to the plastic lens (scratches or cracks) that distort light measurement.
- Degradation of internal sensor elements over many years of heat and UV exposure.
- Wiring harness issues or poor connector contact leading to intermittent signals.
- Incorrect mounting or obstructed sensor field (trim misaligned, adhesive residue, or objects on the dash).
This sun sensor is an economical way to restore proper automatic climate control response on compatible Citroën and Peugeot vehicles. Suitable for professional fitment or competent DIY mechanics, the part number references make it easy to locate the correct replacement for the listed models.
