Very Strange Heater Issue

Been putting this one off for a while now.

Long story short; Hot air will only make its way to the cabin if i have it run through the windsheild defroster vents. If i change only the direction of the air flow cold air flows through the dash and footwell vents.

Surely if it was a heater core or Tstat issue i would not get hot air anywhere?

Originally i thought it was a heater core or Tstat issue because the windsheild vent air takes just a tad longer than it probably should to warm up. No codes on OBD.

Any ideas why it is like this.

Check wheel position under DTC and lock/unlock buttons. Also check for auto air circulation speed.

It took me almost a year to get the hang of my heater.

The defroster button turns the defroster on and heat on high. It also turns on the mirror heaters if equiped. I start to get noticeable heat in about 1 mile this way.

The wheel below the DTC button can be thought as a fine tuner for the dash vents. Red warmer .... blue cooler .... than the main temp setting (dial).

Here's where it gets fun, the buttons for the other outlets .... turn them off. If your feet are cold, turn on the footwell, windshield fogs a bit, top air. The amount of air out is adjusted through your I drive climate menu. It seems BMW has a 'preset' heater configuration that works quite well, the buttons are a quick 'over ride' of the factory presets.

I seldom use 'Auto' but you can try that. The only control you'll have is air inlet (auto, outside, recirculate), dash outlet adjustment and air speed output (through the I drive).

If this doesn't help you may need 'professional' help .... bad cabin temp sensor or something else.

If there is heat in the defrost mode the thermostat is OK. I think you have a problem with the temperature blend door not controling. In defrost it goes full hot so my guess is a temperature sensor or the wiring to it is bad.
David

Thanks. I will look into this later this week. Meanwhile im enjoying my seat warmers a ton!