Finally chilly enough in Southern California to turn on the heat in my '90 Cherokee. While it SOUNDS like it's working, no air is coming our of the vents. A bit is coming out of the DEFROST VENTS but not enough to defrost the windows if I ever had that need in SoCal. (And no, I do not have it pushed all the way to Defrost on the Heat slider.) All of the other settings are working 100%: A/C, Vent. Bi-Level, etc. Just not the heat.

What could be the problem and how to fix it?

Thanks in advance.

 

You stated.. "All of the other settings are working 100%: A/C, Vent. Bi-Level, etc. Just not the heat."
Does that mean when you move the upper control Max blows out the vents strong, Normal out the vents not as hard, Bi-Level blows out the vents and floor, Vent out the vents, Heat out the floor, and Defrost symbol out for the windshield?
I don't believe it is a control problem because if it was it would be defaulted to the windshield only.
The upper control just directs the air to the indicated setting, the lower control determines the temperature. With your rig at operating temp move your top control where you have good air flow out of any of the settings, and move your lower control all the way to the right, you should notice a temp change. If not the first place to check is the blend door (easy for you with a 1990), attached is a photo that is just to the right of the transmission tunnel on the passenger side under the dash. It shows the blend door control rod controlled by a cable, in the photo it is in cold setting if it was in hot it would be all the way to the right against the stop. Find this and while looking at it move your lower temp control slide back and forth, the cable should move the rod. If it does not move likely your control panel is broken, if it does move then it is time to move to the heater core. There are many posts and methods of flushing the heater core.

 

Thank you. Will check this weekend -- that is if the Biblical rain they say is coming holds off until Sunday.

 

 

Thanks!

 

If that's the cause, you owe me an internet beer.

 

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