resharp001

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

Rednroll

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.

resharp001

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".

xanderman12!

Laura Passingham

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.

Rednroll

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.

Dave’s Jeep

it’s not the heater core. You’re not gonna get heat on one side and cold on the other side. If the heater is plugged it’s plugged you’re not getting heat at all.