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Have a 2012 denali and noticed while we were idling the temp gauge started climbing to about the 3/4 mark. Opened the hood and noticed the fans werent on.....turned the AC on and the fans started spinning on low rpm. Turned off the ac and the fans stopped. Got it home and hooked up the obd and looked at torque ffor the actual obd reading coolant temp......i let it idle and the temp climbed to 215 and the fans still would not come on......i pulled the coolant temp sensor plug and the fans came on on high speed and of course it triggered a fault code......So i went to the store and bought a new temp sensor and swapped it out. cleared the code but still doing the exact same thing......i know the fans work ive swapped all the relays and the temp sensor??? what the heck??......are the fans not supposed to come on till more than 215 degrees....that seems a bit high for ust the low speed tonot even kick on.

more testing update.......i noticed if the AC is on it will kick the fans on but they will stay on even if you turn the ac back off and cool the engine down to 200 degrees before turning off again.....if i let it idle all the way too 221 degrees the fans will still not turn on unless i at least turn the AC on for at least a few seconds ....once they engage they seem to do their job then cut off when they should but will not turn back on unless the AC is turned on.....think im going to have to install a separate fan controller
 

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Welcome to the forum.
You'll find a few other threads here which discuss cooling fan problems. The problem could even be in the way the A/C switch controls fan ON/OFF switching. The cooling fan system is rather complex. Look for the link on the forum to download a Lambda-platform service manual (2007-2016 will do). That document would be very helpful. Model year shouldn't be an issue since the cooling fan system wasn't changed much (if at all) through the platform run.
 

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The very first thing to do is make sure coolant is at the proper level. Check it at the radiator, not the overflow (expansion) tank.
 

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The ECM/PCM controls cooling fan operation. It processes information from the coolant temp sensor, ambient (outside) air temp sensor, A/C pressure switch, and possibly others to determine off/on/speed of the fans.
 

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Link to the service manual can be found in a thread of the 'General Discussions - GMC Acadia' section of this forum.
 

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On my 2013 Denali 210 degrees is normal. I do not think I could even see a 5 degree change on the dash gauge. Would not be concerned about it even if I saw it.

George
 
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