Always a good idea to verify coolant temp with an infrared temp gun. 150F-160F coolant temp can make the hoses feel hot to touch but make for mediocre heater performance at best.

I would think bottom rad hose would be substantially cooler than the top rad hose this time of year in Utah. Cool ambient temps remove lots of heat quickly as coolant flows thru the rad.

If both heater hoses are hot, the heater control valve may be restricting flow (try bypassing the control valve.....'97 up it was eliminated) and/or the heater box blend door is not fully opening.

How old is the water pump?.....FSM says a weak water pump COULD cause poor heater performance.

 

I was having the same problem and checked and re-checked everything. Both the inlet & outlet heater hoses were warm so I assumed the core was flowing plenty. I was wrong. Disconnect your heater core hoses and start by flushing from the oulet side (nearest passenger side) so the water comes out the inlet side. Mine ran a bunch of gray water & gunk immediately. After the final flush with a garden hose I removed the remaining fresh water with air from my compressor before hooking everything back up. This fixed my problem.

 

idk if this could effect it, but if the heater hose has a hole in it can it be letting hot air out before it reaches the inside of the cabin?

dont know very much about this kind of stuff

 

Today I took it in for a cooling/heating system diagnostic. The temp gauge is working, the heater control valve is working, both heater core hoses are hot, can't touch them for more than a second. All heater control positions blow a good volume of air into the appropriate places in the cabin.
They didn't mention a specific coolant temperature but they said the gauge was working and it shows just under 210 and remains constant idling and accelerating on the highway. I'll call them tomorrow and ask if they actually checked the coolant temp.
20 degree difference between the top radiator hose and the bottom hose. Radiator temperature dropped from the top left towards the bottom right of the radiator, they didn't mention how many degree drop it was. So, wanna-be mechanic that I am, I don't understand why a 20 degree difference would be bad since the job of the radiator is to cool the water. The shop's suggestion is to replace the radiator but I'm unwilling to do that until I can understand why the temp difference indicates a bad radiator.
Did a manual bypass and there was no change in temp of the air blowing into the cabin. I downloaded a FSM today and it suggests adjusting the blend-air cable as a possible solution but doesn't give a clue about how to do it, that I could find. Anyone know where the door is located? I'd like to see if it's changing position all the way. I've also considered just bypassing the HCAV for the winter but that just delays fixing the problem.
I have no idea how old it is but the vehicle has 146k miles on it. I do know that it's not leaking.

The FSM says to check and replace the t-stat so I'll do that this weekend. Hmm, a little more reading and it says to not replace the t-stat for lack of heat unless a DTC 17 is present in PCM memory. Is that a shop check or can an inexperienced person check for it?

Thanks for all the suggestions and sorry if I got this thread off track.

 

If both heater hoses are hot to the touch with the heater control valve by-passed, then it sounds like the heater blend door under the dash is not fully opening.

 

What is FSM? And how do I bypass heater control valve?

 

Factory Service Manual.......'97 up do not have a heater control valve.

 

Both of my heater hoses got plenty hot yet I still had to flush the heater core to fix mine.

 

Waiting for the weekend and then going ti give it a flush. Then see what happens.

 

Both hoses on the heater core side of the heater control valve must be hot. Heater hoses can both be hot on the motor side of the valve but that doesn't mean the valve is open and hot coolant is flowing to/thru the heater core.

 

I move the slide back and forth from hot to cold and don't hear anything or feel any resistance so I'm thinking this is the next thing to check.

I found a very nice write up on pulling the dash (https://www.cherokeeforum.com/f51/dash-removal-35444/ ) that shows the blend door. That looks like a lot of effort especially since it's snowing now and I don't have a garage in which to work. Is there an easier way to check the cable is attached at both ends and the blend door functionality without pulling the entire dash?

I have a leather seat to put in on the passenger side so I can pull the passenger seat if that will make things easier to reach.

Thanks

 

Sorry, when it comes to the interior, I'm lost.

 

I followed 99 Purle XJ's video link and now my heater is blowing hot air! Thank you! I collected each time I blew the core out in a milk jug and was amazed at the amount I was able to get out of it. I just kept at it till I was satisfied with only clean water. Bring on the sub-zero weather!

 

Turns out my heater problem is the cable from the temp control isn't moving the blend door. I can move the cable end by hand and have instant and very nice heat. Now I can move on the working on the power lock problem.

 

this worked out great. after replacing my bad water pump and radiator i didnt think to flush out the heater core. Sure enough all that crap from the bad water pump was in there. My heat is warmer now.