Jeep heating issue after lots of work

Alext6345

New Member
Joined
Nov 7, 2021
Messages
7
Location
Indianapolis
Replaced Tstat, water pump, heater core and still no heat.

Blower motor works great

Running out of ideas and figured it best to ask for other peoples input.
 
What year TJ? Your Profile is still empty, please complete it. Your problem is probably the flapper door that closes the heat off inside the HVAC enclosure.
 
Search for messages about heater cores. I had 2 issues that caused weak heat. The first was I had to work a bit to get all of the air purged out of the system. I ended up using a funnel that attaches to the radiator to help purge all of the air out of the system (here: https://www.amazon.com/dp/B01A2CQSU6/?tag=wranglerorg-20)

After getting the system completely purged, the heat was better, but it still wasn't great. I ended up having to replace the heater core a second time. After installing the second heater core, and using the no-spill funnel to purge all of the air out of they system again, the heat worked like champ.

I hope it is just a matter of having a bit of air in the lines. Pulling the dash to get at the heater core is never much fun. Good luck.

-T.
 
So, air has been purged to the fullest extent it can be, idles exactly where it should at 195 after another Tstat replacement. Heat has improved, especially when switched to defrost, Its probably around 60 ish degrees. Air door actuator has also been replaced (about a year ago)

Still though, any help would be much appreciated. I do not think it is the heater core, as there are no discernable leaks and it was replaced about a year ago (gave up on fixing it last year). Figured that was an important piece of information.
 
from what i hear on here performance radiators seems to be the only one to use ! the others have a diffuser in the tubes that restricts flow and heat output. do a search somebody here cut one open and showed the difference....
 
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Okay, thank you all for your input. The heat has improved slightly when being driven, putting out about 60 degree temps over what used to be strictly cold.

I am hoping that either swapping the heater core or figuring out whether the doors are actuating fixes the problem.

Does anyone have further details on which doors are known to be troublesome and or which actuators to replace?

Thanks!!
 
I’m having sort of similar issues with my 99 4.0. Thermostat replaced new thermostat housing heater core flush purged air from coolant system. Checked actuators for hvac system. Still not getting to temp used thermostat that was suggested in other forums. Replaced blower motor blend fan and hvac directional switches as well as blower fan resistor. Still no heat or blower fan. What am I missing?
 
I’m having sort of similar issues with my 99 4.0. Thermostat replaced new thermostat housing heater core flush purged air from coolant system. Checked actuators for hvac system. Still not getting to temp used thermostat that was suggested in other forums. Replaced blower motor blend fan and hvac directional switches as well as blower fan resistor. Still no heat or blower fan. What am I missing?
I had heating issues last year. I took the dashboard off and looked at the back of the 'switch panel'/turn dials for the fan, air temp, and air mode (feet, head, A/C, etc.). The left group of wires supplying the fan speed was melted. So I had to replace the whole wiring harness through the firewall but also replaced the switch panel/turn dials thing cus it was 5 bucks and seemed likely to be damaged. No idea why the harness was melted.

Now I'm having heat issues for when its below freezing, the heat is more like neutral temperature air - its not cold, but definitely not warm. If its below zero the heat is slightly cool, so as it gets colder outside, the heat air gets colder. If its 50+ degrees outside the heat blows hot.

This is the thing I replaced along with one of the 3 wire harnesses that attaches to it. But it was less than $10, prices seem to have changed drastically, however this is just the first result that popped up.
https://www.partsgeek.com/gbproduct...MI_pems_C09gIVw21vBB09BApOEAQYAiABEgJIePD_BwE
 
Still not resolved, any further input on potential fixes would be much appreciated.

Was considering taking to automotive place to see if they would do a diagnosis because throwing parts and money at the problem has proven very ineffective haha.
 
There are several threads on this topic you can read over, but I think they all come to the conclusion that most heater cores are a crap shoot at best. From my own experience on 2 different TJ's, I have had to replace the heater cores twice on both to get any heat and neither was stellar. Good luck.
 
Still not resolved, any further input on potential fixes would be much appreciated.
Have you removed the actuator for the blend door and used pliers to manually turn it (the blend door not the actuator)? I'm not too familiar with the older setup but on mine I'd pull the actuator from the bottom and turn the blend door by hand just to double check that the door felt "normal" and it seemed like the airflow was changing. You can also operate the blend thing after you take it out to see if it rotates as much as it is supposed to when you change the dial. This is all 2004 talk so it might be nonsense for an older one.
 
I've done some more reading on the web and apparently a lot of aftermarket heater cores have plastic cores. I'll be buying a new one with metal cores. I know my current heater core is aftermarket, most likely its plastic so I'm guessing thats my issue.

Alex, did you get a new heater core recently?