Your 1998 JGC Limited 5.9 it only blows heat and will not change to ac would this be a blend door issue?

Yes, it is likely a blend door issue. In vehicles like your 1998 Jeep Grand Cherokee Limited 5.9, the blend door controls the flow of hot and cold air. If it’s stuck or malfunctioning, it may prevent the system from switching to air conditioning. Inspecting the blend door actuator and the door itself would be a good next step to diagnose the problem.