windscreen demister

[pjblade1]

Hi Guys.

I have an E83 X3 3.0 sd.

Since i have had the car (& also on my old E46) when you press the windscreen de-mist button on the heater console, (engine temp at normal running) it throws hot air to the windscreen regardless of temp setting on heater console. 

But recently, it will only push cold air to the windscreen. I can get hot air by increasing the temp on the heater console. But shouldn't have to do this. Anyone have the same issue & diagnosis please ?. winter is coming, so want to get fixed asap.

Coolant level ok

temp gauge sits at normal most of the time, but has on a few occasions not got to where it normally sits. (normally vertical 12 o clock) sometimes 10 o clock

[Bimmer Owners' Club]

Hi Paul...welcome to the Forum

I am assuming that it is operating correctly now and was not beforehand.

Most windscreens demist settings are variable as you may only want to keep it lower depending on outside temperature to compensate.

 

[pjblade1]

Hi Trevor. 

Thank you for the welcome.

There is something defiantly wrong with demist operation. 

I have always had temperature display set at 16 degs, both on my old 3 series & this x3. 

Even though this temp is set low. The moment you push the demist button, it fires hot air toward the windscreen. But recently, the only way to get hot air to the screen is to higher the heat setting on the display. It never used to require any adjustment with regards the heat setting. I am thinking it has to be the secondary water pump/valve unit, or the thermostat. The temp gauge always used to sit vertical, & now doesn't quite get to vertical. I don't want to spend out on the wrong part, as bmw parts are pricey

[Bimmer Owners' Club]

Oh I see what you mean, sorry misunderstood. 

If the coolant temperature is not raised enough then that is one issue, however, it could be the heater matrix isn't receiving hot coolant due to it being blocked or similar.

Probably the best way is to get a cheap infra-red temperature gun similar to this link and then probe the hoses to see where it is circulating, or not as the case may be.

https://www.ebay.co.uk/itm/Digital-Infrared-Handheld-Temperature-Gun-Thermometer-Non-Contact-IR-Laser-Point/332426284743?epid=1756017825&hash=item4d66268ec7:g:tZEAAOSwyGZZ8ZGh