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Discussion Starter · #1 ·
Set the temp control at 70° or 80° it doesn't matter. Heat from vents is luke warm. Changed stats using OEM parts. Stack has been cleaned several times (still having overheating issues under load i.e pulling 11k 5r) upper and lower radiator hoses replaced. Inlet and outlet heater core hoses are warm equally but not hot. I'm at a loss. Temp sensor in truck? Come to think of it ac not so cold either but adequate.
 

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2017 GMC Denali 2500HD, 3.5" Rough Country Lift, 305/55R20 Cooper Rugged Trek, Paragon Bed Cover
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What temp is the coolant running at? If you don't have a monitor in the truck, is the temp gauge getting up to the 210 mark, give or take?

If the truck is getting up to temperature, then I would suspect your internal temp sensor could be on the fritz.
 

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Ya, it's running at the fake 210° if I remember right the new stats are 195° and it was checked by a scanner. Is that temp sensor mounted up in the head liner?
 

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2017 GMC Denali 2500HD, 3.5" Rough Country Lift, 305/55R20 Cooper Rugged Trek, Paragon Bed Cover
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I honestly can't remember where that's at. You could also have a problem with the heat/ac control unit too.
 

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Discussion Starter · #5 ·
Actually it's been an on going issue for 10 years. Back when the truck only had 40k. Now it's got 197k. But either I was working in a warm climate or it wasn't bad enough that I bothered to fix it. But now I'm retired and a cold winter this year it's got my attention 😆 :p
 

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Discussion Starter · #6 ·
After researching this site, Google and YouTube with a half dozen places where it might be mounted I finally gave up and called a stealership. So for those who want to or need to know, for this truck it's mounted on the driver's side in front of the radiator. Part # 255775833 or the updated # 15826773. And the wonderful folks at GM decided I need to remove entire grille to access this $3.70 part @ Rock Auto or $14 @ dealership.
 

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2017 GMC Denali 2500HD, 3.5" Rough Country Lift, 305/55R20 Cooper Rugged Trek, Paragon Bed Cover
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But that's your external temp sensor.... there isn't one in the cab?
 

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Discussion Starter · #8 ·
IDK, asked the dealer parts guy for the ambient temp sensor part and that's the 1 he called out. On Rockauto site that's the only one shown.
 

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Yep, now I find out there's 2 temp senors

Does pop out or do I have to remove headliner?
it does pop out but it’s easier to access from above the headliner. I had enough room just pulling it down to reach in and undo it.

FWIW I don’t think your problem is the sensor, sounds like something within the coolant system if you’re also experiencing over heat issues. Is coolant topped off? Have you checked your water pump recently? And when you did T-stats did you purge the system for air?
 
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