Anyone smarter than BMW technicians regarding heater
 

I have a 2012 F10 which recently had light engine came on, that was related to thermostat, after dealer replaced this part, it seems like the heater works only if it has been set to 84 ( I am not sure if that issues was exist before thermostat failure or not). When tempurture set to anything below 84, it will only makes 68 degree heat. Dealer has run the diagnostic test, check the water pump for any leakage but they don't know why the heater only works when it sets to 84. They are researching this issue since past few weeks but so far no luck with any solutions. Anyone has any experience with this matter or suggestion?

Car has 45K milage.

Thanks,

Is this an n20/n26? We've had issues with them getting air bound after tstat replacement. You could try bleeding it by putting heater to max temp, min blower speed and step on the gas for @20 secs. Key on engine off. You should hear the water pump go on. Let this bleeding process complete, maybe 10 to 20 minutes. You might need to do this a couple of times. You could also try to leave the engine running with the coolant reservoir cap off and hold revs at 2500.

Thank you for reply.
It is N20. I performed this bleeding process, but I couldn't hear water pump go on. I tried several times with same result. However, I noticed , if I set the fan to high , then switch to Auto , then let it it run for a minute on auto mode, reduce the temperature on auto mode to lower, then switch back to fan, the blower works fine with adequate temperature.
Even if I do above method on one side (driver or passenger side air control), the blower kicks out correct temperature after this method. It is very strange.
Is it possible the water pump is bad, since this is an electric water bump and some component inside water pump is not functionally correctly, that is why dealer testing is not seeing any problems with the water pump?
Any other suggestions or idea?
Thanks,

I'm not sure why the bleeding process isn't starting. Are pressing the gas pedal down to the kickdown? I haven't had the water pump kick on with this method. Make sure your coolant res cap is off. You should see a stream of coolant. If this doesn't work, something is wrong and the dealer should be able to figure it out.