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Discussion Starter · #1 ·
So I've looked at several threads and and still can't decide what I want to do? The heater core is leaking and fogging up the windows bad. It is not very practical to drive during the winter months. It also seems the ATC isn't working properly as I can't seem to divert the vents from the main dash with both heat an AC primarily going to main vents while also going to defrost -- this causing quick fogging of windshield if I turn on anything related to heat and air. I don't seem to notice a change when directing to floor. The previous owner had installed a light bar switch where the climate control temp sensor used to be in the dash and that really messed with the AC and blend door. I was able to fix that during the summer and now the AC works well as long as the engine doesn't overheat.

1. Should I do full dash removal and AC evacuation to do heater core?
2. Should I bungee up dash and just cut and remove heater core without touching AC?
3. I would like to try and troubleshoot the vents even though fixing the heater core will fix my fogging issue.
4. Can I properly clean and re-seal heater box without removing it?
5. Is there any preferred brand since Mopar seems expensive and almost obsolete?

should I try this and cut out the heater core like some do with 93-96 ZJ?
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Should I take out the whole thing?
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It's not as bad as most people think to pull the dash and do it properly. One weekend and a few beers will do the job.

Your HVAC box, evap core and heater core will be full of smelly crap anyway, which you definitely want to clean out. Improves air quality, lessens chance of windows fogging, and improves airflow through the box.
 

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I’ve done them in less than three hours. We changed a lot of evaporators in the day under warranty.
You can lower the steering column and leave all the wiring hooked up. Unhook everything on the right side and just pull the dash back on the right side to get enough room to get the heater box out. The hardest part was getting the heater hoses off, you can turn the clamps and leave them on, then unhook at the engine and slide them through the firewall to deal with them.
Should be lots of videos on YouTube.
 

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I did my 94 in about 3.5 hours. You should be able to have any local shop evacuate and recharge the system for you for nominal fee. If it's full there should be no refrigerant cost, they'll just put back in what they took out.
 

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As for the hinge method, I honestly can't remember if it's doable with the '96-'98 instrument panel. Most likely yes, I didn't try. Pulling the whole thing isn't that bad anyways, what I did was remove the front seats so that I had more room. I ended up removing the center console, rear seat and floor mat as well, it was a good time to wash the mat. Did some sound- deadening and a bit of cable- routing at the same time.
 

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I'm not saying this as a "don't listen to these guys" type comment, but for the case that you really don't want to spend extra time messing with it. The method of removing the dash top cover and then cutting out some of the plastic above the heater core is pretty easy and is not as much of a hack job as it sounds. I had metal pieces I was going to bolt in to put the plastic back in place with Gorilla Glue or something, but after I saw that the plastic you remove is not really doing anything I didn't bother with it.
 

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I pulled my dash just the other day for this same job (and a bunch of other work as well) and while there are a lot of electrical connectors to separate, as the other have said above, it is not so bad. It is scary to think about but a lot easier that you might imagine. Just take LOTS of pictures and follow a couple threads on this site to walk you through it. Once the dash is out, pulling the heater core is easy. If you are going that far, you might look at your evaporator - at least clean it up - but since your a/c is working good, perhaps not.
 

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Discussion Starter · #10 ·
So I decided to go with the quick and easy hinge method for now. It works well on the later 96.5-98 ZJs. The core was leaking bad but what little I could see of the evap core looked OK. I almost suspect the AC was repaired at some time.

There was a puddle of antifreeze sitting in the HVAC box that I cleaned up along with 1/2 gallon antifreeze under the passenger side carpet.

I cleaned everything the best a could with a 91% alcohol mixed with a little bit of degreaser.

I'm still have weird behavior from the ATC as the AC will randomly cycle even without the AC symbol or when turning on the Climate control and going straight to high heat. I also can't seem to get any significant airflow to the defroster.

I will eventually do a full removal later this winter when I swap to a low mileage 60K 5.2L engine. I need the Jeep running so I can pick up the engine soon.

Removed old heater core and cut tubes with cutoff wheel.
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Doesn't appear to be leaking.
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Not sure why AC comes on when I turn to high heat.
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This is the main display when I set to auto, The AC will cycle even when there is no AC symbol.
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Discussion Starter · #11 ·
So far I found how to read ATC codes and test. The display lights up correctly and I see all the arrows during test but I still can't get the defroster to work. The only code I see is 21 and I haven't been able to find any fault codes lower than 34.
 

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Shew, man, I applauded you for your efforts, but cutting that new heater core pains me.

Both my 97 and 98 turn the A/C on every single time unless its below a certain outdoor temp. Ive not figured out what the exterior temp must be, but it will turn the symbol on then right back off if its cold outside. Otherwise, I have to turn the A/C off manually.

Using the auto setting will always cycle the A/C for humidity comfort. As will the defrost setting. I unplug my high pressure sensor so the A/C doesnt run. Im odd like that.
 

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It's not as bad as most people think to pull the dash and do it properly. One weekend and a few beers will do the job.

Your HVAC box, evap core and heater core will be full of smelly crap anyway, which you definitely want to clean out. Improves air quality, lessens chance of windows fogging, and improves airflow through the box.
I have a friend that lives in Biloxi and he says he never uses the heat just move there, problem solved. No need to pull the dash or anything just completely move to another state. They may or may not have Cheerwine at your local burger joint though. Anyway I would replace it
 

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Discussion Starter · #14 ·
Shew, man, I applauded you for your efforts, but cutting that new heater core pains me.

Both my 97 and 98 turn the A/C on every single time unless its below a certain outdoor temp. Ive not figured out what the exterior temp must be, but it will turn the symbol on then right back off if its cold outside. Otherwise, I have to turn the A/C off manually.

Using the auto setting will always cycle the A/C for humidity comfort. As will the defrost setting. I unplug my high pressure sensor so the A/C doesnt run. Im odd like that.
Thanks for the tip on disconnecting the high pressure switch. I will probably test that here in the dry climate of Colorado. To me it wasn't that big of deal to cut the new heater core. I wouldn't dare try that for the evap core. lol

I did find out that the code 21 is related to the mode door so that explains the lack of defrost. I haven't completely reassembled the dash so I may peel the dash back to get a better look at the mode door. Otherwise I will wait until I start on the engine swap project later in the winter.
 

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21 is a Calibration error. Could be one of the actuators has bad solder joints and is causing that, or could be the actual ATC module has a problem.

 

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I have a friend that lives in Biloxi and he says he never uses the heat just move there, problem solved. No need to pull the dash or anything just completely move to another state. They may or may not have Cheerwine at your local burger joint though. Anyway I would replace it
Yeah.. just using A/C it's very nice to have fresh air, good airflow, and no smell. ZJs don't have cabin air intake filters, just a coarse grill. This is how the evap core very often looks like:

 

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Discussion Starter · #17 ·
Yeah.. just using A/C it's very nice to have fresh air, good airflow, and no smell. ZJs don't have cabin air intake filters, just a coarse grill. This is how the evap core very often looks like:

That is why I suspect my evap core may be newer than 98. I can't see a lot of it but what I can see is clean.
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Discussion Starter · #19 ·
You’re looking at the “clean-air” side...
You probably spent as much time cutting the pipes as would have been to take the 4 fasteners off that hold the box in.
It only took 5 minutes to cut the lines. The AC is working well right now and I needed a quick fix so I can pick up a spare engine. I really didn't want to open the AC lines and buy a new accumulator right now. I have a major project planned and more time when I pull the engine. I also need to pull the front carpet but the previous owner welded 1 leg of the aftermarket seat brackets to the floor. I plan to add sound deadener and wrap the HVAC box when it is down for engine replacement.
 
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