2002 X5 3.0D Interior Heater blower runs on

[john4231618]

Since new, this car has suffered from mystery intermittent battery drain.
Seven, yes-7, new batteries have been fitted! Only now is the possible source of the problem apparent, and this is because the car is parked in a very quiet garage...
The interior heater blower motor runs on, the same as pressing the residual heat button. However, the button has NOT been pressed, and the heater motor runs until the battery is too low to start the engine. This is an intermittent fault, and I've discovered that starting and stopping the engine eventually reaches a point when the heater is shut down.
Anyone got any ideas??