Hi everyone,
I have a 2007 BMW X3 and the heater fan works fine. The upper vents (the top near the windshield) blow nice hot air, but the front and footwell vents only blow cold air.

I already did air bleeding, and the coolant system seems to be working well — heat is good in top vent parts, but the heater only gets hot from the top vents.

I tought it may fault of air distributor damper but the cooler works  perfectly in 3 vents that means the door of air distributir works

Has anyone experienced this before or know what could cause it?

Thanks in advance!

Hi Hamid

Welcome to the Forum

First check the engine bay side there is a distribution valve and Auxiliary water pump make sure it's working. Then inside the car if all fans and controls are working check the Final Stage Resistor (used to be a common fail on E53 X5's) 

Have a look at www.realoem.com put the last 7 digits of your Vin into the search box it should bring up your model, then check the Heater section you should find the FSR (Final Stage Resistor) in the blower motor. You will now have all the part numbers you need to find a replacement at a sensible price. The FSR on X5 E53 models was a fiddle to change but not beyond anyone with a bit of sense

Dave