Smoke from defrost vent & burn smell on 2001 BMW 325i

My 325i has had a fan/blower problem for the past year or so where it will only work once in a while. when it is working it will not blow on low speed, only high. Las nite I cranked up the heat and put the front defroster on and within a minute there was smoke coming out of the defroster vents and the smell was like burning rubber. what could this be? It doesn't happen with the A/C or just the blower with no heat.

Asked by for the 2001 BMW 325i
You either have a bad blower motor or your pulling in dirty outside air from a leaking valve cover gasket where oil is hitting the exhuast manifold. Bring it by when you a chance and happy holidays.
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1 more answer
Have you got the ventilation button on "auto"? You might possibly have a leaking cylinder head cover gasket and the burning smell is drawn into the cabin.
It is also possible a component has failed and emitting an unpleasant smell.
Without having smelt it, i nor dealt it or know exactly what is burning

Best to have it check asap by your nearest BMW dealer or mechanic, which can be located in the "find a shop" tab above.