BMW E39 automatic climate control blows cold air
E39 automatic climate control blows cold air even though the car is hot - what is the fault?
Behind the grille on the front panel of the control unit there is an interior temperature sensor and a small fan that draws air over the sensor. If the fan does not turn, the automatic control gets the wrong temperature. Clean the grille and check that the fan turns; a broken fan is replaced.
Why does cold air come out of the centre dashboard vents?
The temperature wheel on the centre vents bypasses the panel's temperature control. When the wheel is on blue, the air is cold; on red, the heat is controlled automatically. Aim the centre vents upwards, because air directed downwards gives the panel's sensor the wrong temperature reading.
Why does the automatic blow weakly when it should be heating?
The blower automatic is active from startup, even if the AUTO light is not on. Manually adjusted airflow returns to automatic when the blower is set to zero and the climate control is restarted. Raising the temperature increases airflow and lowering it reduces it.
One side blows cold and the other hot - what is the cause?
Most likely the water valve on the driver's side of the engine bay is stuck or broken. Check the valve's connector; a stuck valve can be tapped lightly, which often helps temporarily.