Description
Interior Air Temperature Sensor for Citroën and Peugeot vehicles
The Interior Air Temperature Sensor (part number 643618) is a direct-fit replacement sensor designed for selected Citroën and Peugeot models. This sensor provides the cabin temperature input to the climate control system, enabling accurate automatic temperature regulation, improved passenger comfort and efficient HVAC operation. Ideal for professional workshops and experienced DIYers, the unit is often searched and identified by its product code 643618 — include the code when ordering or searching to speed up identification.
Technical Information
- Manufacturer: Stellantis (Citroën/Peugeot)
- Model: Citroën C4 Picasso (commonly fitted); also used on selected Citroën and Peugeot models
- Product Codes: 643618
- Additional Numbers: Not available
Function
The sensor measures the interior (cabin) air temperature and sends this signal to the vehicle’s climate control module. Based on this input the HVAC system adjusts blower speed, vent blend and compressor engagement to maintain the target cabin temperature. Accurate cabin temperature sensing is essential for reliable automatic climate control performance and passenger comfort.
Common Fault Symptoms
Typical signs of a failing interior temperature sensor include incorrect temperature readouts inside the cabin, unstable or oscillating climate control behavior, inability to reach the set temperature, and reduced efficiency of the heating/air-conditioning system. In some vehicles the climate control may display fault messages or log related error codes.
Why The Part Fails Most Often
Failures are usually caused by moisture ingress, contamination or dirt buildup on the sensing element, connector corrosion, wiring damage or mechanical stress from dashboard work. Thermal cycling and aging can degrade sensor accuracy over many years of use.
Installation Recommendations
Replacement is straightforward for trained technicians and experienced DIYers: locate the sensor in the HVAC housing or dashboard area (often near the evaporator housing or behind trim panels), remove the trim or glovebox as required, disconnect the electrical connector, release the sensor retaining clip and replace with the new unit. Reconnect the connector and reassemble. Always follow vehicle manufacturer procedures for removal and installation. It is good workshop practice to isolate the vehicle electrical system before working on connectors to prevent short circuits or damage to control modules.
Replacement Interval and Service Tips
There is no fixed replacement interval for cabin temperature sensors; replacement is required when symptoms appear or when diagnostic trouble codes indicate a sensor fault. Before replacing, verify the fault by checking connector condition and wiring continuity. After replacement, confirm proper operation by observing stable climate control response and correct temperature regulation at various setpoints.
Notes For Professionals And DIYers
This part is frequently identified and ordered by its product code 643618 — using the part number when searching or ordering helps ensure fast and accurate identification. Fitment may vary between model years and equipment levels; confirm physical match with the original sensor during installation. For workshop efficiency, keep basic trim removal tools, a small pick for retaining clips and contact cleaner available when replacing the sensor.
