Yup that title is right.

My 98 Cherokee Sport struggles to even come close to the normal 210 degrees it should run at. I would say it runs about 140 most of the time even when I try to get it to heat up. Only time it has come close was when I went out to the power lines for a few hours going through a lot of mud which is expected. I lost heat last winter so I replaced my thermostat. Shortly after I broke down due to overheating come to find out my radiator was trashed and I replaced that. While swapping the radiator I did a heater core flush which did have a good amount of build up but was assured the core was fine. Next in the effort was to fix the blend doors but they operated just as they should have. Until recently I gave up and was ready for another freezing winter driving with a blanket and two pairs of all my clothing. I replaced my blower motor resistor which sure enough was covered in a mouse nest and my fan settings work once again. Only problem is is that the air coming through the vents is only warm when you have your hand over the vent. I suspect the thermostat but already? But I will say that my gas mileage is really good. A half of a tank can get me around 150-200 miles. Anything can helps as the temperature out here is falling like a fat kid on a seesaw.

 

Do you have an electric radiator fan or is it the clutch type? If it's electric, is it coming on too early? If it's a clutch type, is it running slowly at first and then speeding up? Is your coolant a mixture of water and antifreeze, and if so, what's the percentage of antifreeze?

 

As you mentioned, I'd suspect the thermostat. I know you mentioned it's been replaced, but new parts fail. I'd start with a QUALITY thermostat.
Do you have a IR temperature thermal gun? Check the temperature difference between the In / Out for the heater core.

You could have a failed seal, allowing cold air into the cabin. My passengers have complained about how cold it is. I also found my glove box to be like an ice box in the winter.

I'd found this low budget repair option. I'm not saying this is the problem, but it might give you an idea. www.heatertreater.net/jeep-cherokee-97-06

In the very near future, I'll be rebuilding the HVAC box & replacing the heater core (not aluminum) & evaporator, in an attempt to heat up the cabin more throughly.

 

Just a guess, but it sounds like your heater control valve is not fully opening.

 

98 model doesn't have a heater control valve, they got rid of that in 97.

 

I have an electric fan and I dont think it's coming on early. The coolant mix is 50/50

 

I definitely think its the thermostat. Just went to the lines again and it got up to 210 and I turned on the fans and sure enough there was great heat. The new one was very cheap so I think its stuck open.

 

Pick up an OEM thermostat. They aren't parts store cheap but are under 20 bucks from the dealer.

 

Test the new one in boiling water on the stove before you install it.

 

So you badly overheated with the new thermostat? Some of the thermostats will fail open if overheated.