Chosen Solution
2000 Nissan Pathfinder blows heat/ac only through defroster vents. No matter what mode I select with the controls it still blows only from the defroster vents on top of the dash & up onto the inside of the windshield. It blows properly hot/cold based on my temperature selection, but will not blow thru floor or face vents in any mode.
My best guess would be a vacuum leak. My 2002 Pathfinder, I think it uses vacuum to open and close the different vents. I can hear it when I change the vents and lift off the gas pedal and step on it, increasing and decreasing the vacuum. A lot of cars use vacuum to operate the vents. On some cars I think the default setting is to the defrost vents, which are the most important to function for safe driving in cold and/or bad weather. The vacuum line might have came off the vent control system that’s mounted in the dash. I’m not sure where the vacuum supply is located. Any who, that’s where I would start looking to fix your problem. Lots a luck. Dan A Arnold
