I have a 2007 EL 4X4 and recently when changing the air temp on the control knob there was clicking sound when the AC temp was turned to its coldest setting. Since then, I have tried the heater and now the air flow only comes through the dash vents and the deforest vents. (no floor heat) Could this be a blend door? an actuator? or a vacuum problem? Are there any relatively simple fixes to this without a full dash disassemble? Thanks in advance