Cooling fans

[SWFLHOMES]

Thought I had an A/C problem but I am told the cooling fans may be running intermitently. Can anyone tell me if there are any fuses or a thermal switch to look for?

Thanks.

[Loren]

From the Cayenne Tech Book

"Coolant temperature sensor

The coolant temperature sensor measures the engine outlet temperature on the cylinder head at the rear left in the coolant distribution pipe. It sends its signal to the Motronic control unit, which passes this information on via CAN. The temperature is displayed by the coolant temperature indicator on the instrument cluster. At a coolant temperature of > 124 °C, the coolant temperature warning light also switches on and switches off again at < 119 °C. The air-conditioning compressor is set to zero demand from a coolant temperature > 117 °C.

Electric fan 1 and 2 for cooling system

Electric fan 1 has a max. power output of 450 watts (when towing a trailer in hot climates 650 watts), electric fan 2 has 300 watts. For infinitely variable control, the duty factor to the end stages of electric fans 1 and 2 is changed from the Motronic control unit, which can be controlled via the actual values. Control of the fan speed depends on:

• The coolant and ambient temperature.

The coolant thermostat starts to open at approx. 80 °C coolant temperature and is fully open at approx. 92 °C. the two infinitely variable fans 1 and 2 are activated at approx. 93 °C and reach their full power output at approx. 105 °C.

• The state of the air conditioning.

If the air conditioning is switched on, the fans are also activated. The max. fan demand is reached from a pressure of approx. 20 bar in the air conditioning. The air-conditioning compressor is set to zero demand from a coolant temperature > 117 °C.

• Above 125 km/h, the speed of both blowers is reduced and is shut down completely at 140 km/h, however, if the coolant temperature exceeds 116 °C it switches back on and back off again below 105 °C.

Fan post-run

To cool the engine compartment when the ignition is switched off, the blowers are switched on depending on the coolant temperature and the last driving cycle (fuel consumption map). The activation threshold is >93 °C or very high specific consumption even on a cold engine. The post-run time lies between 0 and max. 13 minutes, the power consumption is appox. 100 watts. Once the fan post-run has ended, the fans will not re-start with “Engine OFF”. On the Cayenne, the electric coolant post-run pump is also activated via this function. The post-run pump has a power consumption of approx. 10 watts and is located on the cylinder head at the rear and it can be activated by the air conditioning control unit to utilize the residual engine heat."