98 accord vents blow HOT air without fan turned on

Hi,

I have a 98 accord V6, I was driving on the highway the other day, and
the vents started to blow "very" hot air without me turning on the
Climate Control System. This was odd enough, but since it kept hotter
as I drove faster, I tried to turn on the A/C, but looks like nothing
made a difference.

When I stopped the car (with the engine still on), looks like the air
flow through the vents has stopped, then when I accelerated the car
again (with the Fan and the Entire Climate Control System was OFF),
hot air again started to blow from all the blowers in the car.

Any advice on why this is happening is greatly appreciated.

Thanks,
John