Cooling System: Description and Operation

Engine Cooling DDE7

Coolant temperature sensor
The coolant-temperature sensor is bolted to the front of the cylinder head and it picks up the coolant temperature via its changeable resistance.
The coolant temperature serves as a measured variable for the following functions:
- Exhaust-gas recirculation
- Fuel injection rate calculation
- Activation condition for air conditioning system
- Activation condition of the radiator shutter (not MINI)
- Electric auxiliary heater activation condition
- Charging pressure control
- Glow-period control
- Electric fan activation
- Swirl flap activation (not MINI)
- Idle-speed control
- Rail pressure control

Electric fan (not MINI)
The DDE control unit activates the electric fan by means of a square wave signal with a duty cycle of between 5 % and 95 %, thus activating various speeds at the electric fan. The electric fan features its own positive and ground supply.

Electric fan (MINI)
A two-stage electric fan is installed in the MINI. The DDE control unit controls the two stages of the electric fan according to need. The electric fan features its own positive and ground supply.

Radiator shutter (not MINI)
The DDE control unit opens or closes the radiator shutter depending on the operating range.
The radiator shutter opens at:
- Coolant temperature greater than 100 °C (closes at less than 95 °C)
- Speed greater than 180 kph (closes at less than 140 km/h)
- Speed request for electric fan greater than 1600 rpm (closes at less than 1380 rpm)
- Speed request for electric fan by air conditioning system greater than 1600 rpm (closes at less than 1050 rpm)
- Winter safety function:
- Window wipers ON and
- Speed between 65 km/h and 125 km/hand
- Ambient temperature between -8 °C and 2 °C

- Electric fan after-run
- With automatic transmission: transmission temperature greater than 115 °C (closes at less than 110 °C)

During trailer towing, the radiator shutter is permanently opened if the trailer is connected to the trailer module. The winter safety function prevents the radiator shutter from freezing shut while the vehicle is being driven in wet or snowy conditions.

Notes for Service department

Diagnosis instructions

Coolant temperature sensor
The coolant temperature sensor is destroyed in the case of short circuit to B+.
Nominal values for resistance test:
- Resistance at 20 °C: 2.5 - -3.0 kOhm
- Resistance at 50 °C: 0.7-0.9 kOhm
- Resistance at 100 °C: 0.12 - -0.17 kOhm