Rednroll

I have a 2009 JKU and like many Jeep owners I am currently experiencing heater related problems. I've done quite a bit of reading/research and there are quite a few different causes where the conversations tend to go in 5 different directions depending on what others have experienced and their associated fixes and Model Year of JK.

Top causes for JK Heat related problems/Diagnosis of each
RED= Not likely for my problem
YELLOW= Potential problem but not currently suspected.
GREEN= Currently suspect as highly potential cause

1. Casting sand present in radiator cooling system from the factory which gets into heater core and clogs the heater core. (Potential problem, HC was clogged with a fine grey material that felt like very fine sand when rubbed between fingers)
2. Radiator cooling system needs to be burped.(Filled and burped multiple times, slow leak present due to radiator and LIM gasket)
3. Mixture of Hoat and Oat anti-freeze coolants that get mixed and causes a gel to form in cooling system and clogs heater core. (Eliminated, No gel in overflow tank or any of coolant system observed)
4. Failure of blend vent actuator and/or gear stripped (driver's side). (Eliminated as suspect using inspection camera, see post #36)
5. Blend door hinge Failure/Broken. (Eliminated as suspect using inspection camera, see post #36)
6. Heater Core Failure/blockage. (CONFIRMED PROBLEM) [See Posts 50, 54, 64, 67 & 69]
7. Thermostat failure(Eliminated Dash Temp dial does not fluctuate or go above center position once engine is warm)
8. Clogged Cabin Air Filter (Eliminated 2011+ have CAF, I have a 2009)
9. Low antifreeze coolant(Present due to radiator and LIM gasket leaks)
10. Radiator or hose leak (CONFIRMED PROBLEM)[See Posts 42,44,45&49]
11. Radiator cap needs replacing (Replaced, somewhat helped)
12. Lower intake manifold gasket leak (CONFIRMED PROBLEM) [See posts 42 & 52] LIM Fix link: https://www.jk-forum.com/forums/stock-jk-tech-12/coolant-leak-engine-area-343770/
13. Failing water pump (Eliminated, no abnormal noises or leaks from water pump)

My symptoms observed in the order I observed them. Most I've seen reported except for #1
1. (1st observed 1.5 years ago) On Cold days, I can't adjust my vent selector dial to stay on the Defroster setting. What happens is that I can move the dial to the defrost selector, but it won't lock into place. After the cabin warms up after 15 minutes or so of running, then it would lock into place when adjusted to Defrost. Last winter I got in the habit, that after the vehicle was warm to leave the dial on the defrost setting, so that I could defrost my windshield when starting the vehicle in the mornings. Now my heating system isn't getting warm enough where I can no longer do that. I'm able to put the dial on the Defrost/Feet setting and that's what I have to use to defrost my windshield but it takes a very long time to defrost.

[Follow-up Diagnosis and Fix: (See Post #70) Lubricated vent control actuator control mechanism gear and cable on the passenger side.

2. (1st observed this past April). On Cold morning days I will hear a gurgling water swishing sound from behind the dash when the vehicle is 1st started. It goes away after started and doesn't occur on subsequent starts throughout the day and doesn't happen on days when it's relatively warm out.

Follow-up Diagnosis and Fix1: (See Posts 42, 44, 45 & 49). Radiator leak, replace radiator. Leak from driver side radiator end cap. Found using cooling system pressure tester.

Follow-up Diagnosis and Fix2: Broken lower intake manifold bolt and lower intake manifold gasket leak. Replace LIM bolt and LIM Gasket.
(See Post 42, 52) and link:https://www.jk-forum.com/forums/stock-jk-tech-12/coolant-leak-engine-area-343770/


3. (1st observed when very cold temps hit late November). Warm air blows out the vents but the driver's side vent is noticeably cooler.

Follow-up Diagnosis and Fix: (See Posts 50, 54, 64, 67, 69). Partially clogged Heater Core. Replace Heater Core. Heater core seems to be clogged with what looks like it may be engine casting sand. Multiple back flushes were unsuccessful in clearing out clogs. Post #37 is also useful because it seems to show all temp measurements are the same when compared to a properly working heat system, but only driver side vent temp is drastically different.

Thoughts in regards to my current diagnosis vs. the potential causes listed above.
1. Casting sand. I didn't experience any heat problems until after 100K miles. I flushed and changed the antifreeze in August. I didn't notice any sand in overflow or drained fluid from flush.
2. Needs burping. I burped it in August when I flushed the system and ran the heat multiple times and re-topped off fluid since then. I reburbed and topped off coolant in December with front of JK elevated. I no longer have symptom #2, thus seems air is now removed. However, still have symptom #3 where is blowing cold air at idle and warm air at 3K RPMs.
3. HOAT/OAT mix. I have a 2009 that came with HOAT, I flushed it and refilled with HOAT. I'm the only one who has ever touched the anti-freeze top offs and filling.
4. Blend door actuators. This was my #1 suspect diagnosis. What I've read is that the passenger side actuator controls the floor, vent, and defrost switching. Symptom #1 goes away after spinning vent position control multiple times. Driver side actuator controls the cold/warm air blend and fits symptom #3. When I spin the temp dial back and forth quickly, I can hear the blend door open and close. I used an inspection camera and put it through the center driver side vent and fished it down and to the left. I was able to visually see the blend door fully operating using the inspection camera.
5. Blend door hinge. Possible but suspect the actuator since it seems to be a more common problem on JK's. I eliminated this by visual inspection using an inspection camera through the vent.
6. Heater Core. Possible. I noticed my inlet heater hose was hotter than the outlet heater hose. I reversed flush, let heater core soak with CLR and heat was working after this, but then symptom #3 came back after 20 minutes of driving. Possible I have a clog that hasn't been fully blown out and need to redo reverse flush.
7. Thermostat. If I had thermostat problems, it would have seemed I would have had other over heating problems in the summer months and the engine temp seems pretty rock solid with temp gauge in center after warmup.
8. Clogged cabin air filter. I have a 2009, it doesn't have a cabin air filter. 2011 and above have cabin filter.
9. Low coolant. Checked on a regular basis and topped off regularly. I seem to be good. Symptom #2 is now gone, so suspect no air in system and coolant is still full after 3K miles driven.
10. Radiator leak. I took off the top shroud above radiator. I haven't noticed any leaks or coolant around the radiator. Coolant level remains full after filling and driving for 1 month.
11. Radiator cap needs replacing. I replaced the cap and symptom #3 still persists.


Next steps, perform multiple point temp readings using a laser thermometer to isolate reduced heat problem area in circulatory cooling system.

If above doesn't reveal a problem, I am considering purchasing a radiator pressure check system, to see if I can expose any tiny leaks.

Any other thoughts?

[Edit]Diagnostic updates 12/5/17
Problem Solved, diagnosis and fix updates in GREEN Text

ronjenx

The blend door is on the drivers side. It controls the air temp. Does your '09 have an electric actuator for that? My '08 does not.

The mode door is on the passenger's side. It controls where the air goes.

Regarding the mode door, mine did the same thing you described. It would not go all the way to defrost until it warmed up. I now avoid that by running the knob in and out of full defrost several times, whenever I think to do it. It has kept the door free to move through its total travel.

webhannet

A very complete write-up. Having been through heat problems myself, I recognize the kind of madness they can produce in an otherwise normal mind.

Your problems are different from those I have had, Your diagnosis of the heat blend door as a major cause sounds correct. I'm wondering if your earlier ability to move and maintain the defroster position might be due to heating of the plastic making it more maleable. Eventually, it wouldn't move. Probably the actuator was weak - either from the door being "tight" or from failure - and I think may have been the initial problem. I haven't had problems in that area. You might be able to see that area (without pulling everything apart) with a small inspection mirror from below.

Regarding your actual coolant temperature - I think your temperature gauge would tell you if your thermostat failed. I don't think the thermostat has been mentioned in most posts about heater operation, although it was a traditional problem in vehicles. As I mentioned in a previous post, someone told me to run it at 4000 RPM for a couple of miles - and my heater vent output was near 170 degrees afterward. Regardless, I think the heat IS operating differently from when new. I haven't pursued things further, but I think a system flush and coolant replacement should be my next step. I did have burping problems in my previous car (Sebring), and those symptoms were different from my Jeep's.

The complaint of poor heat out of the drivers side is very common and heard more on the older style dashboard we have. My defroster is unable to clear the lower left corner of the windshield in heavy snow. I think the design is just poorly balanced, and poor performance on the left side is to be expected. Complaints of too much heat on the right side are common. I don't have a problem with that, but I suggest stuffing something inside the dash duct to the right side.

If you learn of anything new, please let us know.

webhannet

Reading Ronjenx's post above, it's clearly the Mode Door that's affected.

I don't know if this might work - I bought on EBAY a 25 foot long inspection camera with it's own LED lights. It might be possible to snake it into one of the duct. It was very cheap. I've never used it.

Rednroll

Hmmm?? I don't know. I thought they were all electric actuators until you mentioned yours wasn't. I have a Sahara which usually comes with all the electronic stuff if that helps but I am unsure if the actuator is electric or not.

How can I tell?

Here's a pic of my HVAC controls if that helps at all.

Rednroll

I have an inspection camera I picked up from HF last year so I can give that a try.

I definitely agree with a mode door problem on the passenger side and Ron's confirmation clears any doubt. However, last year when I had the mode door problem I was still getting hot air, so that's why I'm considering I additionally have a problem on the other side as well. However, it is quite possible it failed further but the air flow does switch between the other mode settings. Only the Defrost only setting doesn't work.

karls10jk

2010 and getting mine to roll right over to 'defrost' has been a pain since it was new. I do as Ron suggested- roll it back and forth a couple times until it hangs.

When you pull the center console out and your HVAC controls then you should be able to check that they're manually actuated. One cable swings to the left and the other to the right so it seems odd that there would be an electrical actuator in there-- but I haven't gone further than inspecting the operation of the cables with the unit out.


Side bar- I do not have heat issues to my perception. I've flushed as you have and actually ran heat on full tilt with the electric radiator fan disconnected to try and push the temperatures higher for a (hypothetical) better bleed. I lifted the passenger side of the vehicle higher so the fill port was the highest location and squeezed the hoses while running the heat.

chemlight_ninja

I have an 09, and when I took my hvac center apart to do some wiring i noticed that it is manual. maybe it is binding back there. Another thought, when you flushed your fluid did you flush your heater core? I have had that be a culprit more than once on several vehicles.

Rednroll

Thanks!!! I didn't flush my heater core because I didn't know how to do it at the time.

I found this video last night, and while not a video that is specific to the JK, it does cover all the things to check for heat related problems and how to go about diagnosing each of them. I This gave me a couple more ideas of things to check, reverse flushing the heater core and how to go about doing it was covered. Today's a little warmer outside, so I'm going to try doing some further diagnostics and trouble shooting. I already have laser thermometer, so that should help in diagnosing the inlet and outlet heater core hoses as shown in the video.

https://www.youtube.com/watch?v=-XjXTVJhFLM Does anyone know if our JK's have a heater control valve?

Another thing I'm going to do is bleed the cooling system. My symptom #2 of hearing gurgling water swishing sound from behind the dash indicates that I have air in the cooling system. When I originally burbed my cooling system, I did not raise the front end so the radiator cap opening was the highest point. So this seems like a good place to start of further bleeding the cooling system to ensure all the air is out. Starting around 4:30 of the video diagnostics is where I need to do some further diagnostics.

Does anyone know if our cooling system has a bleeder valve and where it is, if it does?

I cycled the vent cycle switch multiple times and now I'm able to get it to lock it into the defrost position. I just don't have hot air blowing out yet.

So I'm leaning towards these potential problems.
1. Air in the cooling system.
2. Heater control valve problem (but don't know if that exist)
3. Heater core is blocked and needs a CLR treatment and reverse flush.
4. Blend door malfunctioning.

Rednroll

Ok, I think I finally figured out my heater problem.

The past couple days I spent reverse flushing the heater core, and bleeding the cooling system and burbed it with the front end jacked up, ensuring to get all the air bubbles out of the system. I took it for a test drive on the highway, drove it for a couple miles with the engine at 4K RPM and it was blowing out hot air like a mofo. On the drive back home, all of a sudden my nice hot air turned back into it's dismal slightly warm state where I originally started.

I got back home topped off the radiator coolant where it only took less than 1/2 a cup of coolant. Then I look at the front of my radiator and see this.



Does that look like a bad radiator to anyone else?