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I saw something this weekend that I simply could NOT believe and have never seen before in any vehicle I've owned with factory air conditioning.

The air conditioning will NOT operate when the outside temperature is lower than 40F (4C). When you try to enable it, the light blinks several times and goes off. This is explained in the manual.

Out here in the humid Northwest, we use the air conditioner to get rid of the window fogging. Set-up the climate control to blow with heat through the windshield vents but with AC enabled. Works much much faster in the entire vehicle when the air conditioning is enabled. Without the air conditioner it takes longer to defog the windshield and driver/passenger windshields and the rear side windows will be fogged for a long long time. Load a bunch of cold wet soccer players into your vehicle and then see what happens (we play Sept to March). You need every edge you can get.

In essence, you use the air conditioner as a de-humidifier.

I've used this feature in my previous vehicles and dozens of rental cars over the years in winter conditions down to -38C.

What's with this in the Chev?

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Do you have manual or tri zone climate? Are you just pushing the A/C button or are you trying to use the defrost button?
 

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When you set the control to defrost it does run the AC to dry the sir. But I don't believe it runs the compressor as much as when the normal AC is running.
 
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kawazar said:
When you set the control to defrost it does run the AC to dry the sir. But I don't believe it runs the compressor as much as when the normal AC is running.
Just drove my son to school; outside temp is 38 degrees; pushed the defrost button and the A/C button lit
 

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My understanding has always been that when you use defrost the AC compressor is run (unless it is below 40F). This is the way my 04 operates as well.
 

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Just found this in the manual:

(Defrost): This clears the
windshield of fog or frost, more
quickly. Air is directed to the
windshield and side window vents,
with some to the floor vents. In this
mode, outside air is pulled inside
the vehicle. Recirculation cannot be
selected while in the defrost mode.
The air conditioning system runs
automatically in this setting, unless
the outside temperature is less than
4°C (40°F).
Do not drive the vehicle
until all the windows are clear.
 

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GM vehicles, as far back as the 60's when I first started to work on them, have always had a low temperature cut out switch on the AC compressor.
 

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I'm missing something here?

Does the OP have problems with fogging windows when the temp is <40 degrees and defroster does not solve the issue?

Or is the OP trying to specifically avoid running defrosters ( ??? :eyebrow: ) yet still have the fog on the windows minimized/reduced?

I have never had a problem with the defroster's function in <40 degree weather, weather it runs the A/C compressor or not. Once the truck had sufficient engine temperature to warm up the interior and glass, the frost and fog on the inside of the window glass diminished rapidly. If not fast enough, crank the fan on defrost mode for a few minutes until it does.

If the OP is having defroster malfunctions, he should take it in to be serviced. Maybe the defroster ducts were not installed properly or there is something functionally wrong with his truck's HVAC.

--zepcom


PS -- or you could try cracking open the front windows just an inch or two to let wind/air in to have similar effects of drying out your windows?
 

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Discussion Starter #9
zepcom said:
I'm missing something here?
yes ;)

Does the OP have problems with fogging windows when the temp is <40 degrees and defroster does not solve the issue?
The defroster solves it... eventually.

Or is the OP trying to specifically avoid running defrosters ( ??? :eyebrow: ) yet still have the fog on the windows minimized/reduced?
Yes... I use the settings where either the dash vents/foot vents and rear ceiling vents are blowing warm dry (AC dried) air into the rear seats to speed up the evaporation of the fog off the glass surface.

I have never had a problem with the defroster's function in <40 degree weather, weather it runs the A/C compressor or not. Once the truck had sufficient engine temperature to warm up the interior and glass, the frost and fog on the inside of the window glass diminished rapidly. If not fast enough, crank the fan on defrost mode for a few minutes until it does.
As I stated in my OP... "here in the humid Northwest.... Load a bunch of cold wet soccer players into your vehicle and then see what happens (we play Sept to March). You need every edge you can get." It gets foggy enough just from me and my rain gear.

If the OP is having defroster malfunctions, he should take it in to be serviced. Maybe the defroster ducts were not installed properly or there is something functionally wrong with his truck's HVAC.

--zepcom
PS -- or you could try cracking open the front windows just an inch or two to let wind/air in to have similar effects of drying out your windows?
No, you missed the point - the system is working as it was designed. It is a design that has never been brought to my attention in over 35 years of driving but maybe there is a good reason for a design like this.


So thinking a little more on why they would do this, if it -20F outside and you ran the AC, where does the condensate go? It is not going to drain as it will likely freeze in a long drain tube. If you get enough water in the AC housing you may have issues with ice expansion cracking a casing. So it likely is a preventative maintenance measure.

I probably did drive some GM products where the AC was like this but never clued in or, being rental cars, figured them to be broken. I'd bet other vehicles I've driven had a thermostat shutoff as well but unlike the Traverse, they did not have a little red LED that blinks and draws your attention to it. For years all most cars had was a set of sliders and an AC button that lit up.

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This is an uneducated guess, but perhaps another reason is that air below 40 degrees is already dry enough since it cannot hold much moisture due to the cold temperature. This is why you get a lot of static electricity in the winter time, because the air is more dry.
 

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Thanks for clearing it up for me. Couldn't imagine such a 'rainy season' causing so much trouble.

Best of luck finding a solution to your problem.
 

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Carl_NDelta said:
... It is a design that has never been brought to my attention in over 35 years of driving but maybe there is a good reason for a design like this.


So thinking a little more on why they would do this, if it -20F outside and you ran the AC, where does the condensate go? It is not going to drain as it will likely freeze in a long drain tube. If you get enough water in the AC housing you may have issues with ice expansion cracking a casing. So it likely is a preventative maintenance measure.

I probably did drive some GM products where the AC was like this but never clued in or, being rental cars, figured them to be broken. I'd bet other vehicles I've driven had a thermostat shutoff as well but unlike the Traverse, they did not have a little red LED that blinks and draws your attention to it. For years all most cars had was a set of sliders and an AC button that lit up.
Me too. I always thought the A/C was on and working, in all temps. I thought that is what dried the air and cleared the windshields.

This past Monday night I pulled out of my garage with the A/C on and the Chevy's outside temp reading 48 degrees (it was 32 degrees outside). As I drove down the road the temp slowly dropped. It was not till the outside temp reading showed 33 degrees that the A/C On light turned to Off, automagically. The A/C may use a different temp sensor and did not see the change in temp as fast as the dash temp reading (which would explain why the A/C did not turn off when I saw 38 degrees).

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heres some info- that may make sense as to why the ac shut off later...

A little temp reading info...

Outside Air Temperature Display Operation


The outside air temperature is displayed on the Driver Information Center (Fig. , radio or rear view mirror in a number of GM vehicles. There may be some confusion about the operation of the display and how quickly it updates ambient temperature. Depending on several factors, the temperature may not be updated immediately and owners may feel that the display is inaccurate at times.


As an example, here's a look at the operation of the outside air temperature display on several GM small cars from recent model years (2004-2007 Malibu/Maxx; 2005-2010 Cobalt and G6; 2005-2006 Pursuit [Canada]; 2006-2009 Solstice; 2006-2011 HHR; 2007-2010 AURA, SKY and G5; 2008 Malibu Classic; 2008-2010 Malibu).

The ambient air temperature sensor is a variable resistor interfaced to the Body Control Module (BCM). The BCM provides the logic for reading the ambient air temperature sensor, filtering the data and transmitting the information via the serial data circuit to the outside temperature display. The outside air temperature algorithm uses three pieces of information: outside air temperature data, vehicle speed, and the time the engine was turned off.

When the engine is first started, the algorithm looks at how long the engine was off and if the outside temperature is lower than the last reading taken during the previous ignition cycle. From this information, it's determined if a new outside temperature reading should be taken.

If the engine was off long enough or the current outside air temperature is cooler than the stored value, a new outside temperature reading is taken and displayed. If the engine was not off long enough or the current outside air temperature is higher than the stored value from the previous ignition cycle, the last stored value of outside air temperature taken will be displayed.

The outside air temperature will continue to be updated every second as long as the outside air temperature is the same or cooler than the previous reading. Once the new outside air temperature reading exceeds the previous temperature and the vehicle is traveling less than 18 mph (29 km/h), the displayed outside air temperature will remain at its last value. Once the vehicle speed exceeds 18 mph, the displayed outside air temperature will be updated. If the speed drops below 18 mph, the outside air temperature will freeze at its last value.

When using a scan tool during diagnosis, it is possible that the temperature reading on the Tech 2 will differ from the temperature displayed on the DIC/radio without there being a problem with the vehicle. The DIC/Radio only displays the reading being sent from the BCM.



TIP: Do not replace the ambient air temperature sensor or the BCM for an inaccurate outside air temperature display condition.
 

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Rbarrios,

You are a plethora of helpful information at all the right times.

Thanks for taking the time to post this; I learned something new today!

--zepcom
 

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My friend's 2004 Highlander has a faulty AC switch. Sometimes it will work, other times not. I am told this is a common problem with this model. How can I access the switch so that contacts can be re-soldered?

edited by Admin to remove spam link. Behave yourself.
 

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johnywade14 said:
My friend's 2004 Highlander has a faulty AC switch. Sometimes it will work, other times not. I am told this is a common problem with this model. How can I access the switch so that contacts can be re-soldered?
Umm.....wrong forum?
 

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replying late to this. But have had my car for 2 months now. Tonight it was 37 degrees and raining. A/C would not go on and defrost took 5 minutes to clear. Earlier when it was 41 degrees and raining the A/C went on and windows cleared in 10 seconds. This is insane. Non of the foreign cars I have owned every did this. I don't remember any of my dad's old GM cars doing this as well. It's a safety hazard.
 

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tsegway said:
replying late to this. But have had my car for 2 months now. Tonight it was 37 degrees and raining. A/C would not go on and defrost took 5 minutes to clear. Earlier when it was 41 degrees and raining the A/C went on and windows cleared in 10 seconds. This is insane. Non of the foreign cars I have owned every did this. I don't remember any of my dad's old GM cars doing this as well. It's a safety hazard.
Uh, twist the rightmost dial all the way "clockwise" (to DEFROST mode) and put the fan more than "zero". I recommend that you put the heat dial to the red mode too.

Your defroster will then be working as designed.
 

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Yes, this is a problem. The AC will not go on, an leaves all the side windows fogged up. That is the whole point, to draw the moisture out of the car, but with the a/c off and no way to turn it on, it leaves all the side windows fogged up for a long time.
 

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screw991le said:
Yes, this is a problem. The AC will not go on, an leaves all the side windows fogged up. That is the whole point, to draw the moisture out of the car, but with the a/c off and no way to turn it on, it leaves all the side windows fogged up for a long time.

Nice. Karma is -1. real nice. :(

We have no such issues with our defroster with heat mode. Sorry if I offended. This will probably be the last I'll be around here for a while.
 
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