So the heat/vent/defrost won’t produce hot air, just cold (unheated). Both hoses are hot, so the core is fine. Temperature **** has an electronic module on the back—is there a motor-operated damper or actuator that has gone bad, or could it be that module behind the **** (hope it’s this, because it is easily accessible).

If you put your head in the passenger side footwell and look up under the dash - where the carpet ends toward the transmission tunnel - you will see the blend door motor. It’s on the bottom of the big black plastic HVAC box. There is a pivot that attaches to your blend door (full open for hot, full closed for cold, and in-between to “blend” temperature). Turning your hot/cold **** with power on, you should see the motor turning that pivot.

If nothing is happening, it could be the ****, a bad motor, no electricity, or I suppose the door could be jammed. Having google-investigated this issue myself, it seems like the most frequent culprit is the motor.

Here’s that electric motor and pivot, 99-01.

Thanks for the great info. This Cherokee is on its last legs, and getting through one more winter with heat would be fun.