If I turn it to blow out of the dash vents, sometimes it will sometimes it will blow out of the windshield defrost vents AND only the top of the side front dash vents (part that blows on the door windows). If I want just to blow the vents and it doesnt work if I raise the tempature a couple degrees the front vents will cut on. But if I lower the temp again it will stop, and start blowing out of the defrost vents again. Any help.???? Or I am just missing something on how to control the ac system?? Thank you for any info