On two occasions the inside, front passenger side floorboard of my 2011 suburban has become extremely hot. No smell of antifreeze/coolant coming from the heater core. But there is sufficient wetness from what appears to be condensation because of the heat.

I've had my local dealer check for the cause but they have been unable to duplicate the problem. Which usually happens after long trips at highway speeds.

Any advice as to the cause and solution?