Why Ac Quit Working?

[Black4x4Z71]

We've owned out 2011' 4x4 Silverado for a couple weeks now and we are still learning

about how much different it is to our old 2003' 4x4 Blazer.

 

Early yesterday morning it was very cool out and when I started up our truck.

The outside temperature was displayed in the dash as being 34 degrees which

felt about right. Later in the day, we were pushing 70 degrees when we I pushed

the AC button no cool air came on. The light just flashed a few times then went

out again. The outside temperature readout in the dash was still showing only

34 degrees. I looked in the owner's manual and it said that if the outside

temperature was below 40 degrees it will not allow the compressor to engage,

this explained why we had no no cool air flow but why didn't the outside

temperature sensor not adjust to the higher temps outside?

 

I called the dealer today and the service rep explained that the newer cars and

trucks required higher driving speeds to push enough air volume over the temp

sensor in order for it to sense the temp changes. He said that just driving

around town at 30 mph will not create enough airflow to the sensor to create

changes in the temp display. WTF?

 

I told him that our old Blazer had a very active outside temperature sensor and

was accurate just sitting still in the driveway. He said that about 3

years ago GM went to this new sensor system and it now required more airflow to

motivate the temp sensor. In fact, he said that yesterday a lady drove in and complained that her AC would not work on her near new Buick. He went for a ride with her and they

drove out of town up to highway speed and the display quickly adjusted the warmer

outside temperature and once it showed above 40 degrees, they were able to turn

the AC on and it stayed on!

 

Tonight when we got in the truck the temperature display showed 60 degrees so we went for a drive on the highway and watched as the display in the dash quickly zoomed from 60 degrees to 75 degrees to match the actual outside temperature.

If this is what is required to get accurate outside temperature readout, this system was poorly engineered. Heck, the old system worked great just sitting in the driveway. I may still insist that the dealer install a new sensor just to see if it makes any difference.

 

Has anyone else experienced this with their late model GM truck or car?

[05GMCZ71]

You probably needed to take it out of Auto Mode then press the AC button, then you can kick it back into Auto and it should keep AC on.

[Black4x4Z71]

You probably needed to take it out of Auto Mode then press the AC button, then you can kick it back into Auto and it should keep AC on.

 

 

Yep, I tried that too. It would not work in manual or auto mode because it thought that the outside temperature was below 40 degrees. This is not a bad feature and keeps you from freezing up your system, unfortuinately it was over 65 degrees outside at the time.

[dewfpo]

I wonder if it's the location of the sensor or the sensor itself. Also wondering if you could just swap out the new sensor with the older model?

 

DEWFPO

[nickvrebel]

I would imagine, and this is pure theory here, that a good reason for this is to prevent the temp read out from being skewed horribly high when sitting in stop and go traffic. When sitting in traffic in the summer especially, the temps in the area of the grille and engine compartment get much higher than outside air temps, so giving you that number would not be accurate. This is just a theory, sounds like while it could help in that situation, it had a negative effect on the activation of a/c.

[dewfpo]

On a previous car I had the ambient temp sensor was located at the bottom of the drivers door mirror. Seemed to be pretty darn accurate all the time.

 

DEWFPO

[Silvercolorado]

Hi everyone,

This is my first post. I have a 2011 Silverado and had the same problem. First, the dealer changed the temperature sensor. Didn't work. Next they changed the HVAC control module. That didn't fix it. Next they found a bad connection in the wiring harness. It still didn't work correctly. Finally they rechecked the bad connection and reprogrammed the computer. That fixed it. After the four trips to the Dealership they were sick me and I was sick of them. Note: They told me the same thing about it having to be driven above a certain speed and distance etc. I would drive it like they said and then I would pull in to the dealership and the sensor would read 31 degrees or so when it 64 outside. They could't argue with that. Mine is not totally accurate all the time, but the temperature sensor will change when parked now and I am happy.

[sabre364]

Drive over 30 mph for over 5-10min. if it doesnt start updating then, there is an actual issue. Those aren't the exact numbers (might be 20 and 8 mins or something). Stupid design. Chrysler does it too. If you leave your car overnight, the numbers will update on startup as you know, but if you are taking a ton of short stop and go trips all day, it will still read the morning's temp since not enough time has elapsed since last start sequence.

[palukie]

If you want to test it out yourself , locate the sensor and use a hair dryer to heat it up and see if the ac kicks on.