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Discussion Starter #1
Hello Jeepers! I ask with humility for your help. Yes, I have searched, but can't find the answer to my issue.



2012 Jeep JKUS
115k miles, service more than regularly




The hot air on the driver side is not blowing nearly as hot as the passenger side. The passenger side is blowing at @ 125* and the driver side @ 85*. :pullinghair:



I tried to remedy the problem as many have suggested by back washing my heater core hoses under the hood and I cycled water through the input hose and output hose about 3x each. I refilled the input hose with 50/50 and connected the hoses back up. Still no hot air on the driver side.



I checked the actuator and the air flow mechanism: both work as designed and the AC comes on and the vent, floor, defrost all blow when selected.


I took my cabin air filters out, and tried it, no heat on Drivers side. I put them back in, no heat on Drivers side.


If I get the Jeep to operating temp, turn off the Heater/blower and let it site for 5-10 minutes, then turn the heater/blower back on, it does blows heat from the driver vents for about 30 seconds, then cools again to 85*



I am at a loss as to what may be the issue. I've thought of switching the inlet/outlet hose under the hood to see if that will help the flow, but that is a last resort.



Any help is greatly and warmly appreciated! (Pun intended!) Thanks.

:drinks:
 

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When my 2013 was having the same symptoms 4 or 5 years ago, the dealer replaced the heater core. It was plugged (Probably from manufacturing casting sand). It fixed the problem. But If yours has lasted this long, it might not be the same issue.


dp
 

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Discussion Starter #4
Sounds like the HVAC blend door actuator is wonky

I got under driver dash and had my son go from heat to cool and the actuator door moves in full motion. It seems to be working fine. It seems too if this was the issue, it would still blow hot equally on all sides, but perhaps not really hot due to the AC/Heat mixing. I'm really only getting heat on the passenger two vents.



Thanks
M
 

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The problem is still most likely a plugged heater core. I experienced exactly what you have. I flushed it with water several times and it didn't fix it for long. My driver's side "heat" wasn't being warmed at all.

I did fix it though without replacement. I purchased a heater core flushing gun off Amazon. It's basically a garden hose gun with an attachment to connect to heater hose and a compressed air port. It works - you need compressed air to force all the sand/sediment out of the core. Normal water flow often won't do it.

To flush, you reverse flow water through the core as you have done, however you periodically stop the flow and use 1-2 second bursts of compressed air. This will forcefully blow all the water out of the core, and take lots of sediment out with it. You repeat this until those bursts no longer produce any sediment.

I had to empty the bucket I was using frequently towards the end to verify whether sediment was still coming out. This process completely fixed the issue. I ended up using this gun, with some modifications to fit larger hose, to flush the engine block and radiator when I did the whole cooling system. Works very well.

Buy a metal flushing gun, the plastic ones are garbage and will leak. It's not expensive. If you don't have an air compressor, it'll still be cheaper to buy an inexpensive one than replace your heater core. Even if you're replacing the core yourself, the labor involved is extensive.

There are mods out there that reduce heater core replacement labor by cutting some of the dash's metal support structure and the aluminum heater core tubing and replacing it with rubber hose. Personally, I'd stay away from this. Metal tubing is used in the cab for a reason - it's safer. If, and given enough time when, that rubber hose fails the passenger foot well is going to be sprayed with hot coolant.
 
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Discussion Starter #6
The problem is still most likely a plugged heater core. I experienced exactly what you have. I flushed it with water several times and it didn't fix it for long. My driver's side "heat" wasn't being warmed at all...

Thank you! I did use some compressed air with water, but was afraid to use too much air pressure in the system. I guess I will buy some more 50/50 and try it again, but with water/air mixture.



I may even try to switch the heater core hoses at the engine compartment and see if that helps after flushing too.
 

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It's unlikely you'd actually be able to exceed the burst strength of the core doing this. Since you can get water to flow through the core, it's definitely not completely plugged and pressure can only spike so high.

When I did this, I ran water through at full pressure and once it was flowing out for a few seconds I'd use an air burst to empty it and then do it all again. It honestly took an hour, maybe a little more, of doing this before I wasn't getting anymore sediment. The flushing gun makes it a lot easier because you're not constantly switching between water and an air hose.

I wouldn't run the core with a reversed flow because that might reduce performance. It's supposed to enter from the bottom and exit the top, this helps keep air from getting trapped there.
 
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Mike,
I had the same problem with my 2014 JKU. Heat was 160 p,lus on my passenger side, and 85 degrees f on driver side. Dealer told me my heater core was plugged. NO heat on drivers side because that side of core is further from the heated tube side of core, so its the first to plug. He stated that the cylinder head on the 6 cyl engine is made in mexico, and is made with a sand casting process. Further, the factory there didn't do a good job of rinsing the sane out of the cylinder head. End result is that sand can go through the cooling jacket passages in the whole engine, and eventually settling in the lowest part of the system, which was my heater core. (There are other older posts reporting blocked radiator tubes.) The estimate involves removing the dash, pulling the steering column, removing the center console, the plenum etc to access the heater core. The past is less than $200 but the total estimate was between $1500-$1700 NOT counting replenishing the a/c system if refrigerant was lost. I appealed to Jeep corporate, the original warranty was expred. I had a non factory bumper to bumper warranty from Portfolio (Bought this Jeep used at a Jeep dealer). My dealer advised me that Portfolio declined the claim as they specifically exclude BLOCKAGES. Shame on me, they knew of a problem that I did not. I paid the dealer to flusch it out. They sed AIR which did nothing. I instructed them to use a top of the line flush. They did, and 2 weeks later my problem recurred. (Heat on passenger side was over 160 degrees, on drivers side and driver side defrost was 85 degrees in winter time here in NY.) My local independent mechanic did the whole job for less than $900 , again installing Mopar coolant. Problem solved.

There are repairs on other threads where owners her cut the heater core suppy tubes accessing it through the plenum under the dash. I wanted the proper repair as I want to keep this Jeep for many more years. BTW this happened at around 90,000 miles.... still not time to change the original coolant under the Jeep recommended service schedule
There is at least one class action law suit suing FCA over this. The class is in Ohio and I wasn't eligible to join it as a plaintiff.

Today I again got only cold air while driving in 50 degree weather (was 95 yesterday) Just my luck, now it's the actuator door. How I made sure it wasn't the heater core again? I felt both heater core water lines (aluminum tubing on left side of engine, coming from water pump area, partly visible under the plastic engine cover near back of the engine. BOTH sides are hot,meaning water is circulating well. Mechanic hooked it up to a diagnostic computer which states that blend air actuator is not functioning. Going back into shop at 1 pm today. Hoping for a quick repair, we have a wake today and funeral tomorrow in my home town for an NYPD officer killed in the line of duty that I must attend.
 

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Air in the system will cause uneven heating through the vents too, so make sure to rule that out before you go to town replacing cores and all the rest of that.


If your overflow has been empty for a while you would be sucking air into the system and enough air will cause the issues.
 

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Air in the system will cause uneven heating through the vents too, so make sure to rule that out before you go to town replacing cores and all the rest of that.
Some JKs left the factory with air in the cooling system leading to performance issues. OP, if you're still on the original coolant and I assume you are, I might just do a complete cooling flush to clean the whole system out and make sure it's air free. I know you're not due for another 35k miles, but coolant's not that expensive and you'll be able to flush out any sand/sediment that may be in there and will eventually migrate to your heater core anyway.

You don't need a lot of tools to do this and there's a sticky on the forum with a procedure. Something to keep in mind when paying shops for this kind of thing - you don't really know what they're doing or how much time they're spending to do it right, and this is the sort of issue that can get expensive fast if you're paying a shop to troubleshoot, especially since they have every incentive to tell you the only way to fix the problem is with a heater core replacement and a 2k bill.
 
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Discussion Starter #11
Thanks All, I am going to try to work on it again here soon. I think I will use the air/water mixture to clean it out and run water through it for a longer period of time.



I also plan to use a T connection (from one of the flush kits) on the higher/input Heater Core hose and see if I can get air out as I fill it to the max through the hose connection on the T. (if that makes sense).


@Bob Sanders, you may be onto something as I did have very low fluid in my reservoir and I would assume some air was sucked in....


Thank you all for the tips, now to go and work on it more...after lunch.
 

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Discussion Starter #12
Welp,



Blew out the heater core. Added CLR, let it sit in heater core for 5min, ran water through the heater core in a backwards flow in the output hose. I added an engine flush T to the input hose so I could "bleed" the hoses of air and add fluid to the radiator. There were actually bubbles coming out of the input heater hose as I filled the radiator. I refilled the reservoir and blew out the hose from radiator cap to reservoir, no blockage. I though all is well and this is going to work.



It did not....Still no head on the far L Drivers vent.....so lame! Errrrrrr
 

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Did you use the compressed air to repeatedly force water through the core? It's that violent movement of the water through the core that will break up the blockages, and it generally also has to be done repeatedly. When I did this, I actually used hot water from a hot water feed in my basement and used a garden hose to transport it out of the house.

This is the flush gun I used: Thexton THX815
 

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Plugged Heater Core.
 

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Inlet vs outlet

Guys,
Please help me identify the inlet from the outlet on jk 2013. I want to back flush correctly.

Thanks
Seg
 
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