i have been having trouble with my heat for quite some time and just recently flushed the coolant with not even the slightest bit of improvement. i have read stuff about the blend door being a possible problem...how can i find this out for sure and how much would this cost to fix??? i have also had some weird burning smells coming into the cabin but when i turn the climate control to off, they go away....could these problems be related? (i already changed the cabin air filter) any help or ideas would be awesome...thanks!