Jump to content

Too Hot Too Cold HD Denali


Recommended Posts

Looking for a little feedback. 2016 Denali HD (Duramax, Crew Cab).

 

I put the HVAC controls in manual mode, temp setting at 68, air direction at bi-level, fan at ~30%. Truck is at operating temp; I typically drive 80 miles/day in semi-rural settings.

 

Sometimes my feet will sweat, sometimes they are cold. Same for the rest of me too. Putting my hand up to the dash vent, the air will feel extra hot or cold corresponding to that particular "feeling". More often than not, it's "cold" feeling.

 

I am not running it in "auto" mode. I don't trust automatic mode based on my history with my previous 5 GMC vehicles. When I have briefly tried Auto on this truck, it didn't seem to be consistent either, so running in manual mode, I would think, would be more consistent.

 

Now that the outside temps are starting to drop, this is more noticeable, especially the cold feeling. Just to be clear, it seems to vary from time to time, changes as speed changes and outside temp varies.

 

My 12 HD (SLT) does act this way. This 16 has been in the dealership for other issues for ~18 days now and I've been in three loaner Sierra 1500s (SLE trim, 2 double cabs and 1 crew). Those 4 trucks, with the same settings, behave "as expected". Temp seems consistent. If it feels too hot, I can click the temp setting down to 67 and it "feels" ok, too cold, click it up one.

 

Since this is such a subjective topic, I resorted to buying a thermometer with a "meat" style probe on it with digital readout.

 

Temp on the dash vent (with settings set as above) vary from 81F to 54F. Sometimes it will be 72 when at a stoplight, then travel down the road and temp will drop to 62. Sometimes it will climb to 78 or 81 and stay there (uncomfortable while driving). Click the temp setting down to 67 from 68 and the one time it dropped to 55 (38F outside) and stayed there until I clicked back to 68 ('cause I was getting too cold).

 

Do the Denali trim level change the temp output even when in manual mode? The owners manual indicates the air temp can change based on a bunch of sensor inputs but implies this is only automatic mode.

 

Just to be clear, I am not doing temp checks and trying to compare them against what the dash setting is just to see if they are the same reading, I'm checking these because the truck is not staying consistently comfortable inside and I'm trying to see if it is "just me".

 

Any insights, similar behavior, resolutions, suggestions for proper testing, etc?

 

Truck is currently at dealership for this and another issue. It sounds like they are going to say "works OK, must just be you not knowing how to use it" based on the phone call yesterday. Mechanic also stated he had a '14 that "you have to run in auto mode" when I was explaining the issue to him.

Link to comment
Share on other sites

  • Replies 31
  • Created
  • Last Reply

Thanks for the replies.

In regards to auto mode, my 95 didn't have it, my 99, 02, 03 and 12 did and I never found it that useful. It frequently felt like the fan was blowing too much air at my face/upper body a lot of the times and running in manual mode solved that - and the temp felt just fine.

 

I did run auto mode on the last loaner '16 (SLE) and found it was OK - BUT - I also found manual mode to work acceptably on it as well.

 

So back to this Denali... Picked up from the dealer tonight. The tech discussed the HVAC item in depth with me. Truck was in for service for an exhaust leak (turbo inlet gasket was replaced) which was causing "raw" diesel fumes in the cab at idle.

 

Tech indicated truck passed all tests and was operating normally.

 

Tech indicated that the HVAC monitoring/sensor and operation on the Denali is _substantially_ different than even an SLT. Don't know this myself other than to say that is what I was informed. Anyone know otherwise?

 

According to the tech, my issue is that I have put the truck in manual HVAC control mode and now it is trying to attain the set temperature but is limited on the fan speed, the truck is "wildly" adjusting the output air temperature to try and compensate. He didn't feel the truck should be putting out continuous 55F degree air from the vents when the temp setting was lowered from 68 to 67, but did a "relearn" on all of the HVAC systems which he thought may have helped to solve it.

 

His solution is to use "automatic" mode as it will allow the system to work as designed; he specifically recommended against putting it in manual mode citing it as the cause of the issues I was experiencing.

 

He indicated one of the sensors is on the dash and that the dash was an acceptable place to put a thermometer if I wanted to pull a temperature reading versus what I was "feeling". I had specifically enquired on this as I had thermometer readings from the console area that read 60F when the temp was in manual and set to 68F.

 

A lot of what I'm describing in detail is "colder" temps, but I have similar "too hot" readings as well. I'm just more tolerant of riding in a too cold truck than when it's too hot.

 

Let me restate - I was perfectly content with the HVAC operation with my 2012 SLT (107K miles that I've driven it) and the three loaners (2015 SLE, 800 miles), 2016 SLE (500 miles), 2016 SLE (300 miles) that I've had over the last month. I realize this sounds like a whiny little b|tch talking when we get into the "my porridge is too hot". It's very subjective, which is why I resorted to checking my "feels like" data with thermometers in the cab.

 

On the drive home from the dealer in this Denali tonight (45 min, generally rural highway) I left it in automatic mode as instructed. Temp set at 68.

 

I put the thermometer on the dash (no vents blowing on it) after 10 minutes of drive time and left it on while driving. It felt a little cold in the cab (it was room temp from coming out of the service stall, but was feeling cooler the longer I drove it.

After 20 minutes, thermometer indicates 63.1F (temp is on auto, set for 68F). 10 miles later, I'm still feeling colder, so I click it up to 69F. Definite change in temp is felt overall and what is coming out of the vents. Thermometer bumps to 64. About 5 miles later, it's too hot (seriously, the warmer air never seemed to taper off), so back down to 68. Thermometer drops to 63. Temp resumes to feeling cold. Unfortunately, I didn't put the thermometer near me to get a reading on what the temp was when it felt too hot. I did do so at the end of the drive when it felt a bit too cold and it read 64.1F. At the end of the drive, thermometer is at 62F on the dash. Again, it feels colder (than what I expect 68F to feel like) to me in the truck.

 

Anyone with a 15/16 Denali that runs in colder weather that feels the HVAC works as expected (it's ranging from 15F to 50F in this area now)? According to the dealer tech, I can't compare behavior with anything other than a Denali trim.

 

62ina68.jpg

Link to comment
Share on other sites

Minor update.

 

2 thermometers in the truck, one on the console in the wireless charging spot and the other on top of the dash just left of center.

 

In AUTO mode, set to 68F. 38F outside temp, no sun. 45 minute trip on rural 2 lane, average 62MPH.

 

Temp reading from dash thermometer was down to 59F, one on the console was 64F. This was at the end of the trip. Both started out a bit warmer, the dash thermometer was ~63 when I started the trip.

 

My feet were starting to feel cold. I had redirected the dash vents so they were not blowing directly on me, which seemed to help me feel not as cold overall.

 

Going to see if I can rig up some temp sensor data loggers and determine that either I'm just nuts or this truck is not working correctly.

Link to comment
Share on other sites

Sorry to derail this thread a bit, but I noticed your radio "interface" looks WAY different than mine. Is this a standard in the Denali's or is it because my truck is a 2015i? Anyone know.

 

"Standard" Denali, 2016. The loaner 2015 SLE I had for a week or so was very similar on the radio, not sure if it was a later '15 or what.

Link to comment
Share on other sites

 

"Standard" Denali, 2016. The loaner 2015 SLE I had for a week or so was very similar on the radio, not sure if it was a later '15 or what.

Interesting. Maybe it's a gmc thing then. The actual interface looks a bit different on mine. It also doesn't display the little xm logo and the buttons up top and favorites look different.

Link to comment
Share on other sites

I think it's because the heater/ AC isn't that sensitive as a degree at a time. I think it varies on/off like every 3 degree even though it says one on the gauges.

Link to comment
Share on other sites

I have 2015.5 and mine seems to do the samething, doesn't really matter what the outside temps are.

 

Set auto at 69 and it is either just right (most of the time) or it is freezing. Bump up to 70 and it becomes real toasty in the cab. Back down to 69 and it will freeze you out.

 

I have not taken back to the dealer to look at since it does not do this all the time.

Sorry to derail this thread a bit, but I noticed your radio "interface" looks WAY different than mine. Is this a standard in the Denali's or is it because my truck is a 2015i? Anyone know.

Mine radio looks just like his radio

Link to comment
Share on other sites

I have 2015.5 and mine seems to do the samething, doesn't really matter what the outside temps are.

 

Set auto at 69 and it is either just right (most of the time) or it is freezing. Bump up to 70 and it becomes real toasty in the cab. Back down to 69 and it will freeze you out.

 

 

I'm still doing data collection over longer periods of time (have 4 temp probes set up with laptop doing collection), but what I've seen for sure, is in AUTO mode, the truck usually puts heat out on the floor and the temp down on my feet will increase by 10F when adjusting the dial one degree. It stays at that elevated temp until the dial is adjusted. I haven't done enough testing to give more solid info (does it increase/decrease linearly, etc.).

 

See the attached graph for an example (1000 seconds = 16 minutes). I'm running in full Auto mode at 68. Feels drafty around my upper body, so I click the temp from 68 to 69 at around the 1900 second mark, where the temp spike happens. The temp at my feet jumps 10F (78F) and continues to climb slowly until the end of the trip. The temps being monitored on the graph are dash, console, floor and rear seat. Not worth reading too much into this one graph on all the readings, other than to show what the floor temp is doing. This seems to explain why it goes from feeling cold to "too hot".

 

floorTemp.png

Link to comment
Share on other sites

If it makes you feel any better I HATE auto mode, I don't want the fan blowing like crazy for no reason, I don't even want to hear the fan or have it drying out my contacts, if the heat is on the fan is turned all the way down and on my feet.

 

Besides that auto mode seems to run the a/c non stop and there is no reason for it.

Link to comment
Share on other sites

Not sure about gm, but in Honda manual mode the number is pretty much useless. It's just an 'about', or a rough guess. The low and high numbers are extreme changes, ex. 61 can blow kinda cool, 60 will move the mix motor substantially and will blow much cooler, same with 89-90. In between are slight changes, but aren't accurate in relation to the number.

The number is used mostly in auto, as the in car temp sensor will run the system whichever way in needs to keep the temp at the desired number.

I also hate using auto, I'm ok with a low steady air blowing, not hot one min, cold the next, and blower speeds all over the place.

When in manual you pretty much have to just use it like the old red/blue dial, not based off the digits. Of course my experience is with Honda, so take it for what it's worth

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Forum Statistics

    245.8k
    Total Topics
    2.6m
    Total Posts
  • Member Statistics

    333,236
    Total Members
    8,960
    Most Online
    Lightning123
    Newest Member
    Lightning123
    Joined
  • Who's Online   2 Members, 0 Anonymous, 705 Guests (See full list)




×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.