Thermal Mapping of the Cooling Fan Relay in a Citroën Berlingo: Causes of Overheating in Urban Driving

Understanding the Overheating Problem in the Citroën Berlingo

The Citroën Berlingo is a versatile vehicle, widely used for urban logistics and light cargo transport. However, its intensive use in cities—characterized by stop-and-go traffic and heavy congestion—puts a lot of strain on the cooling system (the set of components responsible for maintaining the engine at the correct temperature). The most common symptom reported by owners is the temperature gauge rising rapidly or the STOP warning light illuminating on the dashboard during traffic jams.

Often, the culprit isn’t the radiator or the water pump, but rather a small electrical component: the cooling fan relay. When this component fails, the fan (the ventilator installed in front of the engine) doesn’t turn on at the correct speed, preventing the heat exchange necessary to avoid engine overheating.

The Role of the Relay and System Architecture

The electric fan operates via commands sent by the Electronic Control Unit (ECU). For the fan to rotate, the electric current must pass through a relay — a type of electrically controlled switch. In the Berlingo, the system usually operates at two speeds. The first speed is activated when the engine reaches an initial operating temperature, while the second (stronger) speed kicks in during critical situations or when the air conditioning is turned on.

Overheating occurs when the relay suffers internal wear or when its base melts due to excessive heat, interrupting the flow of energy to the fan. In urban driving, where there is no natural headwind to cool the radiator, failure of this component is fatal to the engine’s health.

Main Causes of Thermal Failure in Relays

• Oxidation due to moisture: Due to the location of the relay box, close to the front grille, the ingress of rainwater or engine wash water can cause corrosion on the pins (bluing).
• Wear and tear due to electrical fatigue: Constant activation in urban traffic causes the relay’s internal contacts to experience small electrical arcs (sparks), increasing resistance and heat in the area.
• First Speed ​​Resistance Burned: When the resistor that helps control the low speed burns out, the system tries to compensate by switching directly to high speed, overloading the corresponding relay.
• Undersized Wiring: In older models, the wiring may become dry, generating excessive heat that melts the plastic housing of the relay.

Diagnostics and Fault Codes (DTC)

To identify the problem, it is essential to connect an automotive scanner to check for error codes in the injection system’s memory. The DTC (Digital Trouble Code) helps guide the repair.

• P0480: Indicates a fault in the control circuit of electric fan 1 (low speed).
• P0481: Indicates a fault in the control circuit of electric fan 2 (high speed).
• P0691: Low voltage in the fan circuit, suggesting a blown fuse or a relay shorted to ground (negative wire).

In addition to the codes, a visual test can be performed. With the engine cold and off, locate the relay box near the radiator and check for signs of melted plastic or a burning smell.

Component and Fuse Location

In the Citroën Berlingo, the cooling system protection fuses are usually located in the BSM (Boîtier de Servitude Moteur), which is the fuse box located in the engine compartment, generally near the battery. The main fuses are usually 30A (Amperes) or 50A, depending on whether the fan configuration is single or double.

The specific relays for the fan are usually located in a small plastic box attached directly to the fan bracket, protected by a cover. They are 4 or 5 pin relays, with capacities ranging from 35A to 50A.

Step-by-Step Guide to Verification

1. Initial Visual Inspection: With the car off, open the relay box cover in front of the radiator. Check that the terminals are clean.
2. Fuse Test: Locate the power fuse in the engine housing. Use a multimeter (a device that measures electrical quantities) on the continuity setting to ensure it is not blown.
3. Drive Simulation: Start the vehicle and turn on the air conditioning. Under normal conditions, the fan should turn on within a few seconds. If it doesn’t turn on, the problem is with the control unit or the relay.
4. Resistance Measurement: If the fan only turns on at maximum speed when the gauge is almost in the red, test the part called “Fan Resistor,” which is usually located next to the relay.

Parts and Maintenance

When replacing a relay, always use components with the same amperage. Using low-quality relays can cause fires in the wiring harness.

The costs for this repair in Brazil vary. A good quality relay costs between R$ 40.00 and R$ 90.00. The resistor costs between R$ 120.00 and R$ 250.00. Adding the specialized labor, the complete cooling system repair service usually ranges from R$ 350.00 to R$ 700.00, depending on the complexity of the wiring damage.

Necessary Tools

• Automotive multimeter.
• Torx keys (a common standard in French vehicles like the Berlingo).
• Electrical contact cleaner spray.
• OBD2 scanner (optional, for reading codes).

When to Seek a Professional

If you notice that the plastic connectors where the relay fits are melted, simply replacing the part won’t solve the problem. You’ll need to replace the connector and redo the wiring soldering. In these cases, or when the problem involves the BSI (the car’s internal electronic control unit), it’s recommended to take the vehicle to a workshop specializing in electrical systems or in PSA vehicles (Peugeot and Citroën).

Conclusion

Maintaining the thermal system of the Citroën Berlingo in good working order is fundamental to ensuring the longevity of the 1.6 or 1.8 engine. Relay and resistor mapping should be done preventively every two years or whenever you notice unusual temperature gauge readings. Small electrical faults ignored in urban traffic can result in serious cylinder head damage and very high repair costs.

Disclaimer

This article is for informational and reference purposes only. The content published here was compiled from publicly available technical information and general market references, and does not, under any circumstances, replace the diagnosis and intervention of a qualified mechanic or authorized dealership. The website is not responsible for any damages, losses, or consequences arising from the practical application of the guidelines described here. Always confirm part numbers, torque specifications, and procedures in the manufacturer’s official manual before any repairs.