I have a 1990 jeep Cherokee Laredo w the 4.0. I have only had it a few months but it has not had any heat since I got it.
I did do my research on some common reasons as to why my heat might not be working and I understand how my heating system is supposed t work. The blender door is not an issue. The heater control valve works (currently). Even flushed out my heater core and it was not as terribly dirty as I thought it would be. I asked the shop to take a look it a week ago from today. They said the HCV was not getting the vacuum and said I could just use a zip tie to hold it open for the time being and so I did. Even though the HCV did not work at the shop, it is working on its own right now. Either way you look at it, the HCV is not an issue. Waited at the shop with the mechanic to make sure it was gonna get hot and it never did. They suspected it needs a new heater core. I then explained that I flushed it out and they said it could still be partially clogged. They quoted me $600 to replace it and I can't have that done right now. Decided to do it myself and I just got done installing a brand new heater core. Well, guess what!! Still no heat!! I will say the air that does come out is just a tad bit warmer when it's on heat than it is when it's just on air. And the HCV is currently working on its own. When I feel of the heater control outlet(s) only the bottom is hot and I mean it is hot! However, the top one is not really warm at all. I feel that my cooling system is not connected correctly.

 

[QUOTE=Byronator;3662921]I have a 1990 jeep Cherokee Laredo w the 4.0. I have only had it a few months but it has not had any heat since I got it.
I did do my research on some common reasons as to why my heat might not be working and I understand how my heating system is supposed t work. The blender door is not an issue. The heater control valve works (currently). Even flushed out my heater core and it was not as terribly dirty as I thought it would be. I asked the shop to take a look it a week ago from today. They said the HCV was not getting the vacuum and said I could just use a zip tie to hold it open for the time being and so I did. Even though the HCV did not work at the shop, it is working on its own right now. Either way you look at it, the HCV is not an issue. Waited at the shop with the mechanic to make sure it was gonna get hot and it never did. They suspected it needs a new heater core. I then explained that I flushed it out and they said it could still be partially clogged. They quoted me $600 to replace it and I can't have that done right now. Decided to do it myself and I just got done installing a brand new heater core. Well, guess what!! Still no heat!! I will say the air that does come out is just a tad bit warmer when it's on heat than it is when it's just on air. And the HCV is currently working on its own. When I feel of the heater control outlet(s) only the bottom is hot and I mean it is hot! However, the top one is not really warm at all. I feel that my cooling system is not connected correctly.[/QUOTE

It's a little confusing in you post what's going on with the heater control valve but if the inlet is hot and the outlet is not and you have a new heater core I would bypass the valve .

See
https://www.cherokeeforum.com/f2/wha...-valve-230998/

 

So I got rid of my heater control valve today. Bought some new heater hose, a splitter, and even a manual valve. Easy job! wish I had tried this before replacing m,y heater core. At least now I have heat!!! Thank you for the advice.