i have i 1998 cherokee sport 4.0 4x4
problem:
the heater blows warm air but not hot and does not blow very hard..
yes both heater core lines are hot and the cable the switches from hot to cold also works.. the fan also works in all positions and blows properly when in the cold setting..just when in the warm setting it seems like something is not letting the hot air threw or only just a tiny bit, but just to the point by the time it comes out it is just luke warm never enough to get the cab warm.

any one have any idea what could cause this??

 

found a thread on the same thing .. with answer