Check the plug on the firewall below the batter tray single red w/white tracer. That is the blower motor hot wire it has a case ground.
The heater control panel I think 4 screws. Pull it away from the dash slowly. The lever that turns power on to the system uses two white wires check for voltage at both sides and then move the lever make sure power goes through. If you have power there on both sides go over to the passenger side and look at the heater vents you should find a plug going to the resistor that gives you the three speeds. Check for voltage there with a meter.
Here is apic of the blower motor wire and plug
89YJ 2.5L TBI, AX-5, NP231 SYE, Tom Woods Shaft, 33" BFG T/As, 4" lift.
AF Jeep Club Tail #184