Okay guys, I've been searching everywhere to see if anyone else has the same issue as me. I have a 99 XJ, 149k miles. My heater only blows hot air on the first 2 settings. If I turn it to 3 and 4, it becomes likewarm/cold. No clue what could be causing this. Any help would be greatly appreciated!

 

Check both heater hoses to see how hot they are at operating temp. Both should be equal and HOT.

 

Blower motor resistor. I have had the same issue for a while, just never got around to fix it. Mine only works on 1 & 4. Local parts store should have them in stock and they are fairly simple to replace!

*** Edit: I read wrong. Thought your fan was not blowing on those settings. Sorry!

 

This^^. Your heater core may need flushing.

 

I have flushed the heater core several times, have replaced tstat also. Both heater core hoses are hot.

 

Could be a blend door issue. Not sure how the '97+ XJ's work. My'96 is cable operated where as later years I believe are all vacuum operated.

 

97+ are stepper-motor actuated.