Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Air Flap Control: Notes
The air flap control regulates the air supply for the engine and assemblies cooling system by only opening the radiator shutter as it is needed.
Up to 2 radiator shutters can be installed in the front end.
Conditional on the present design envelope, the engine version and the engine management system, there are the following versions of the air flap control:
- Passive air flap control via electromagnet
- Active air flap control via actuator motor (radiator shutter drive)
- Active and passive air flap control (radiator shutter drive for the upper radiator shutter and electromagnet for the lower radiator shutter)
The required design envelope for the active air flap control means that it cannot be combined on some models with certain optional extras (e.g. Sports package, active steering or active cruise control). The passive air flap control for the lower radiator shutter must be eliminated in some models with turbocharging.
The illustration shows the upper and lower radiator shutter in the E90.
| Index | Explanation |
|---|---|
| 1 | Upper radiator shutter |
| 2 | Radiator shutter drive for the upper radiator shutter |
| 3 | Front end |
| 4 | Lower radiator shutter |
| 5 | Electromagnet |
The engine management system (DME or DDE) continuously calculates the required cooling output and only opens the radiator shutter when an increased amount of cooling air is actually required (DME stands for "Digital Motor Electronics"; DDE stands for "Digital Diesel Electronics").
While the vehicle is being driven, the closed radiator shutter shortens the warm-up phase of the engine, as operating temperature is reached more quickly if the environment is better encapsulated.
The air flow through the radiator creates high aerodynamic drag as the driving speed increases. In higher road speed ranges, the closed radiator shutter improves the aerodynamics. This reduces fuel consumption and thus the emission value.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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