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Heat works only on passenger side

 
Old 01-03-2019, 01:41 PM
  #21  
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Drove my jeep to work today. After driving about 30 minutes home, my readings with full heat and recirculating were 130.6, 145.5, 149.5, and 146 working from driver's side over to passenger side. That is a heck of a lot cooler than that 170* you're getting! Seems to correlate with the left driver's side being the coldest vent though.

**now I'll be wondering if my heater core is about to go kaput
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Old 01-03-2019, 06:23 PM
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Originally Posted by resharp001 View Post
Drove my jeep to work today. After driving about 30 minutes home, my readings with full heat and recirculating were 130.6, 145.5, 149.5, and 146 working from driver's side over to passenger side. That is a heck of a lot cooler than that 170* you're getting! Seems to correlate with the left driver's side being the coldest vent though.

**now I'll be wondering if my heater core is about to go kaput
For an Apples to Apples comparison, take the measurement as such.
- Fan blower speed=low
- Recirculate=off
- Temp=Full heat
- Front vent only selection
- Parked

From the pic I posted previously, you can see my settings match above if you're more of a visual individual.


I would venture to guess, your HC is fine. The most likely reason your readings are on the low side is because you were moving, and the blower was on high. The reason why it's lower is because there is more fresh air being pulled into the system from outside. The more fresh air coming in, the more the HC has to heat and therefore the more the HC will cool down. Kind of like your radiator fan, it goes into high speed when the engine temp is higher to suck more cool air in through the radiator to cool the coolant inside the radiator faster.

I recently helped someone else on another forum with a heat related issue and I provided them the same steps above to follow for their measurement. They came back and mentioned they were in the 150F range and were concerned their HC wasn't up to snuff as well. Come to find out they also had the blower on high when taking the measurements, and once they put the blower on low and re-took their measurements, they were in the 170F range. Based on your temps being similar with a similar measurement method, I'm betting your temps will be good as well. I'm sure most tend to take the measurement with the fan blower on high due to instinct telling them that's when the most heat blows out of the vents. While that's true it's not the best setting to get an apples to apples comparison measurement because the amount of outside air and outside temperature will have a bigger impact on the actual temp of that temp reading.

Last edited by Rednroll; 01-03-2019 at 06:37 PM.
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Old 01-04-2019, 12:21 PM
  #23  
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Not to have hijacked this thread, but I think it's interesting information that many can benefit from. My results weren't in motion, but I did have recirculation "on" and the fan was on "high". What you said makes sense. I will test again this weekend with recirculation "off" and the fan on "low".
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Old 01-22-2019, 05:57 AM
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Default Significant problem with heat

Originally Posted by smorris67 View Post
2009 JK - heat only works on passenger side - blows cool air on drivers side
this is a very well known problem with jk jeeps and should have been a recall. There is now a class action lawsuit. This will be my last Jeep due to Chrysler not taking action and righting their problems
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Old 03-15-2019, 12:02 PM
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Originally Posted by Rednroll View Post
Yes, mine was blocked with casting sand.
To add to this, here's what I feel is happening. Even with the majority of my HC caked with casting sand the inlet and outlet hoses had the same temp readings which originally made me think my HC was ok. Even with a brand new HC, what I found is that the driver's side vent will always blow cooler than all the other vents. I found it was 15-20deg F cooler once my heat was back to fully working good. The air has to travel furthest from the HC to reach the driver's side vent than any of the other vents and that air also passes over the blend door to get to that vent (there's very cold air directly behind that blend door in the Northern winter areas), so that's my theory on the reason the driver's side vent is always slightly cooler. Just loss of heat of the air due to thermodynamics of distance traveled and flowing over a cold surface (ie the blend door). Anyways, the heater core is about 12inx8in in area. With a partially clogged heater core the area of the HC which is actually getting hot is drastically reduced (think of it as now having a HC which is 3inx8in in actual area) and therefore the driver side vent will still be coolest but since it's 20deg cooler to begin with, it will be the most noticeable where you will feel cold air blowing out of it. Since the HC is not fully blocked when caked with casting sand, coolant will still pass through it and that is the reason the inlet and outlet hoses will measure the same temp as is what I discovered. The problem is that the hot coolant is no longer able to flow through all the slots inside of the heater core to be able to fill the entire HC. In the example above with the gel, it is likely many more of the tubes inside the core were blocked and is the reason for the inlet/outlet hose temp differences. Gel material is just much more easier to back flush out of the HC stuck in those tubes than casting sand which is packed inside of those tubes.

At least that's my theory and I'm sticking to it. I've had others doubt my theory and when I asked them for a better one they couldn't provide one. As many know I've spent a lot of time diagnosing my heater related problems, and I dissected and inspected my clogged heater core once I removed it, so I've grown pretty familiar with how the heater works in our JKs, so I feel pretty confident with my theory until someone provides a better one.



Please help. I have read many threads on this. I have a 2011 JK. Heat on passenger side cool air on driver side
I have had heater core flushed 2x worked for about a week. Then I got the HC replaced worked for 2 weeks again same thing is happening
I'm sooo pissed. I'm not sure what to do at this point.
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Old 03-16-2019, 04:39 AM
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Originally Posted by Laura Passingham View Post
Please help. I have read many threads on this. I have a 2011 JK. Heat on passenger side cool air on driver side
I have had heater core flushed 2x worked for about a week. Then I got the HC replaced worked for 2 weeks again same thing is happening
I'm sooo pissed. I'm not sure what to do at this point.
Based upon what you mentioning that it worked for 1-2 weeks after having a HC flush done, and a HC replacement then I suspect your heater problems are not related to the heater core.

Check my diagnosis thread linked below, especially the 1st post which I have updated as I was diagnosing. In there, I have identified 13 of the most common causes of heater related problems of the JK. Unfortunately, everyone of those causes can create the symptom of cold air coming from the driver side vent. So just because you have the symptom cold air from the driver vent, it doesn't always mean you have a heater core problem, although that is one of the most common failure problems.
https://www.jk-forum.com/forums/stoc...roblem-339178/

Based upon what you described, my best guess at this point is that you have a coolant leak somewhere in the system. The reason I say that is because after performing a HC flush, it then requires the coolant system to be refilled and the system burped to remove all air. The same thing needs to be done after a HC replacement as well. If there's a leak, then the coolant will gradually leak out and introduce air into the system and depending on the size of the leak, that will take 1-2 weeks to happen which is what you are witnessing.

Therefore, I would start by checking your current coolant level. If the coolant level isn't filled all the way to the top of radiator and the overflow reservoir isn't filled to the max fill line, then you should top those off and burb the system. If your heat comes back after doing that, then you know you have a leak in the system and the next step becomes finding where the leak is occurring. The most common causes of leaks are from the radiator, thermostat housing, and lower intake manifold gasket and that would be the order I would start checking for leaks. The best way to find the leak is having a pressure test performed.

Another possibility based on what you described is that you may have the mixed OAT/HOAT coolant problem going on which causes gel to form inside the coolant system. The gel could clog the Heater core in 1-2 weeks time if present and a HC flush or HC replacement would have temporarily fixed that problem. If you have the gel problem, then you should be able to inspect the bottom of the overflow tank and see if you observe gel sitting in the bottom of it. If that ends up being the problem, then you will need to have all the coolant drained and an entire coolant system flush performed.

Last edited by Rednroll; 03-16-2019 at 04:57 AM.
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