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2020 gmc denali HD has heat but right vent on drivers side blows cold. Tried cycling the system through all its functions with no change. Just the 1 vent will not blow heat the dealer said the actuator doors are working and want to remove the dash to replace the heater core. All the other vents blow heat just not the right drivers side so I thought it was unusual to replace the heater core. Any insight is appreciated

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I'm not knowledgable enough on this to be given credibility, but something tells me you're correct.  If the problem was the heater core all the vents would have cold air blowing out of them.  It does sound like one of the blend door actuators are not working.  However, as I indicated at the beginning of my post, I don't know enough to know for sure.

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Well, just as a FYI, not the same Vehicle but my Wrangler blows hot on passenger side and cold on drivers and it's a very well known problem with Wranglers., the heater core gets clogged on one side and the vents that go to the drivers side go across the cold side of the Core and blow cold air, hot air on passenger side, replaced the heater core and problem solved. With that being said I find it hard to believe that a heater core in a 2020 truck could be clogged but I guess it's possible.

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