How to fix Jeep Cherokee XJ blower not blowing (Diagnose relay or resistor)

In short, if it works only on setting 4 it is more than likely the resistor $30ish dollars at Autozone or even less on Rockauto. If the fan comes on intermittently, only on the lowest setting or not at all check the relay it’s a generic 5 prong 30 amp square relay cost about $10. If that still doesn’t work check fuses, and wiring wiggle to see if you can get it to come on, and lastly replace the blower motor if all else fails.