electronic or manual aircon?
either way the temp control gate is located under the pass side dash. if manual might be a broken cable or fell off the connector. If electronic-- several things to trouble shoot.
the hot/cold slider just opens the valve...there might also be a door somewhere that is not being activating...I don't think pulling the dash pad will help you at all...you're going to be more down in the footwell area.
pulling the pad won't help. I t might help to pull the computer out( don't unplug it) just to get the extra wires out of the way. If there is no tension I'd bet either the calbe broke or one of the lock tabs came off. they are simple c clips there is one one the end under the dash and another behind the controll pannel center dash. I'd put my money on the clip breaking before the cable since there isn't much tension to start with.