2012 Tri-climate with reduced or no heat

[AstralRT]

I am having more issues with my 2012 R/T 3.6 AWD w/Tri-climate

 

Now that things are getting cold I've noticed that there is limited to no heat from front passenger side including front side defrost vent and very limited heat from driver side center vent.
There is heat from the driver side by the door and floor, rear vents and front side defrost vents but ONLY when coolant temp reaches above 90°C (194°F) , problem is when the colder temps below 0°C the coolant temp drops to low 80°C (176°F) when driving.

I suspect multiple problems, just looking to bounce this off the knowledgeable experienced folks on this forum.

For the passenger side I suspect a bad actuator door as the cold A/C was blowing perfectly fine during the summer.

For the temp dropping so low when driving I suspect a thermostat stuck open, however I never watched the coolant temp this closely before there was a problem so I'm not sure if dropping to low 80s is normal?

 

My coolant level is not low, in fact its a shade higher than normal.  I haven't checked the heater core lines, I'm not familiar with where they are located the DJ.  Are they only accessible from up top or can I get to them underneath? Are they very delicate to work with?

Would a clogged heater core cause these issues? Do you think I should flush the heater core? Is there something else that might be causing these symptoms that I haven't listed? I've heard the oil cooler could have impact on getting no heat too but not sure how, aren't they on different coolant systems?

[2late4u]

you could do a reverse heater core flush. look on you tube for heater core quick replacement video.i would start with the thermostat replacement first as it would be the cheapest, find both the heater core hoses before they go Thur the firewall and see if they both are hot and warm or hot and cold, and i did just have a friend that spent a bunch of money fixing a no heat problem they replaced everything including the heater core and then she said they finally found out it was the oil cooler unit causing the problem i dont see how it could be that but the oil cooler does run coolant thur it as well.... good luck and keep us informed

[AstralRT]

Any idea if the heater core lines can be reached from above without taking parts off the engine?  Its too cold to want to be crawling underneath the car now

Edited December 6, 2019 by AstralRT
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[2late4u]

you tube has some great videos on how to do a quick and easy way to replace a heater core on the drivers side on the journeys