How hard is it to pull the dash and replace the switch I the fan only blows on low.
I need to know the year, model, engine and if the A/C system is manual or automatic so I can help you better.
If you check the continuity of the switch on all positions you can determine if the switch is good or bad. You may have to go further and check the blower resistor (for manual system) or the blower module (for automatic system.
The more information you give me on your Jeep and problem the better I can help you diagnosis the problem.
Get back to me when you can with this information.