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Suburban HVAC Issues

Vehicle - 2005 Suburban LS, 5.3L V8; manual slide temp controls, separate controls for driver and passenger sides.
Issue - In winter drive side vents will suddenly switch from blowing hot air to cold air. Just the opposite happens in the summer with drive side vents suddenly switching for blowing cold air to hot. Interestingly the passenger side vents operate normally. Sometimes if I stop and restart the vehicle the system will start working properly again but this does not always work. Before I take it to the shop I would like to have some idea as to what the problem could be. Any help greatly appreciated.

Was the problem coincidental with an occasion for the battery to be disconnected? ie new battery etc. I have read of other problems, thus use a memory maintainer and in what I have read replacement of the actuator is the only solution. Should be less than $500

Wouldn’t you know when the HVAC system breaks it does so in exactly the wrong way! Cold air in winter, hot air in summer. Sigh. Sorry you are having this annoyance. I don’t have any experience w/your make/model but most vehicles these days have either vacuum or electric motors (actuators) that move the venting doors. And it seem to be a pretty common thing for these to fail to get the job done, especially the electric stepper motor version of the HVAC actuator. If yours uses the vacuum actuators, it is possible a vacuum line has come loose either in the engine compartment or under the dash. If electric, either the actuator is bad or the computer system which does this function is confused about whether the door is open or closed. Sometimes the fix is that the computer has to be re-learned, usually requiring the manufacturer’s scan tool.