[wsouthb2]

Help please!!

My 2012 E93 335i N55 shows an overheat problem after about 20 miles of motorway driving. When it does this, the bottom radiator hose is stone cold. So i initially thought it must be the thermostat, so resigned my self to replacing the waterpump and thermostat. However, I then noticed that even from cold, the cooling fan was acting erratically various speeds etc...I've now found that if I start and drive the car with the heater control panel off, I do not get any issues and the bottom radiator hose gets nice and hot. Everytime it shows an over heat problem, I get a code "ECU has requested the electric water switched off due to blockage" I assume the blockage is the thermostat being shut? The most obvious question is has anybody come across this? Is it possible its the software in the heater panel corrupt? How does the heater panel interact with the thermostat? and any other answers you may be able to throw up. Car has done 70k miles and not sure if it's ever had water pump or stat. I should add, that with the heater panel on, although i know it will eventually go into limp mode, the heater and aircon all work fine.