Thanks for the mention Dutch...I'll see if I can help our chap.
Getting back to the OP (who may or not be a cook), let's start with the simple stuff first (free). Make sure you have the code for your radio written down, then open your drivers door and leave it open. Next step is to disconnect the battery and go and make yourself a cup of tea and chill out for 30 minutes or so. Then reconnect the battery, start the motor and let it idle while you go through all the airflow settings and see if you get the flow going where it should. If you have the overhead display thingy, you may notice that all the previous settings might need to be entered again, but that's just a normal thing, PITA, but normal. If everything is working the way it should (airflow wise), take her for a decent drive (at least 10 miles at this time of the year) and pay particular attention to the temp gauge which should sit at, or around 90 (needle vertical) and the air temp from the vents.
Still crappy? Now comes the bit which might cost a few bob.
If the temp gauge needle is much less than 90...mine was reading about 25...the thermostat and its housing needs replacing. If this is the case, your fuel bill will bring a huge smile to your face.
However, if all of the above stuff I've written makes any difference, the next step is to replace the little fan pack resistor that Dutch mentioned...not very expensive, easily sourced and fitted and readily available on Ebay, or a supplier of your choice.
If you have to resort to the resistor pack, just remember the battery steps I wrote above...never do any electrical stuff on a Jeep with the battery connected. Then you'll understand about the radio code bit.
Let us all know how you got on...you have an audience now.
