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AC Questions

biochemist

By biochemist
in Ask A GM Technician

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biochemist Enthusiast

biochemist

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Hi GM-Tech...I have a couple questions/observation about my AC. I just tested with a thermometer in the middle vent...here is what I observed, I have the dual-auto setup BTW:

 

Temp and Humidity at the time of testing 80 F and 80%...quite sticky, cloudy...

 

Full fan, recirc, 60 degrees both sides...temp at vent after 5 minutes = 62 F

in auto mode ~ 60 F

 

While driving it will drop a few degrees to ~55 or so F

 

However, if I lower the fan speed to ~ 1-3 bars the temp can gets as low as 40 F, very chilly! Seems to put out cooler are at lower fan speeds.

 

Also, can you tell a difference when in recirc mode versus not...I sometimes hear something move in the dash area, but at high fan speed I cannot tell a diff. in fan speed or sound. It does cool better when that button is pushed though...

 

I guess I am not understaning how this system works...I typically to not use the AC, so I cannot remember how it was last year when new, but I thought I remembered it being a tad cooler. Not that it does not cool off, but at Max fan speed it seems to not be pumping out COLD air, just cool air...is the system functioning OK, I mean, it will go down to 40 degrees at lower fan speeds just does not pump that cold of air at max speed (all while not driving BTW)...While driving it seems to cool down a touch better, as expected though. I think the system is function OK as far as the auto goes, if I move up to 61 degrees it will adjust the fan speed and it will pump out hot air on one side and cool on the other, so that partioning function is fine...Last thing, even if it has been 100 degrees, it will pump out cool air almost immediatley after starting...so I am not sure, figured I would see what you guys thought. Thanks, later, :D:):chevy:

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted

If you switch between recirc and normal, you should hear a change. If recirc is not working, that will make a big difference in vent temperatures.

biochemist Enthusiast

biochemist

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If you switch between recirc and normal, you should hear a change.   If recirc is not working, that will make a big difference in vent temperatures.

 

 

 

Thanks GM-Tech...I only notice that sometimes the bar count will increase by one...funny that this morning (80 and 80 again) the temp was ~55 out the vents and ~48 after driving for a while...at half max fan speed got down to 37 degrees...the whole cab was a condensor at that point, windows all condensed on the outside of the truck. The interior was down to 56 degrees!!! I think it is working fine, sometimes I hear a door shut or something like that sometimes I do not when hitting the recirc button. I assume since I almost froze this morning all is fine? It is so humid here...but as looks like it is fine though. I think the Auto climate control does what it wishes...I noticed if you put it down to 61 (not 60) it will back off and try to make the cab 61...which it did...I could tell that it was blending in a tad warmer air to raise from 56 degrees...and after a few minutes it was right at 61-62....So, I assume you would consider the system to be working normally as the system can blend in warmer air? That means the recirc must be allowing for this warmer air to be added in? On these auto systems, there must be a graded opening of the vent door to allow warmer air to be mixed in, it cannot be just simply open and closed or how could it maintain the temps so well from 60 (57) all the way to 90? I know on manual systems (like my wifes Equinox) when the recirc button is pushed I do hear a difference in fan speed...I cannot tell as well on my silverado though, but it does raise one bar sometimes depending on the temps, settings and such...? I am not sure how it really works, help me out with some of your tech data or something...If the recir door was not moving the light would not stay on, right? The system must have sensors for this, and I also notice a temp drop when I press the button, a few degrees while sitting still, so it must be working? How long to cool the cab, 2-4 minutes, I do notice reving a bit seems to cool even more as well as driving, but this is to be expected as the compressor is driven by the engine...anyway, Let me know, thanks, later, :D:):chevy:

biochemist Enthusiast

biochemist

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You lost me somewhere in the middle there, but it sounds like it's working fine.  :D

 

 

 

Sorry, a little long winded...but I was wondering, as long as the recirc light stays on, this means the system (recirculation) is working? I notice the AC will blend in warmer air if not set all the way to 60...as my cab was 57 and I set it to 61 on the display...I noticed the air was a touch warmer, so the ac must be letting in a bit warmer air to get it up to 61 that quickly, which is where it ended up...I notice a temp diff between record and regular AC, but not really a fan diff...anyway, the system about forze me this morning and it is super humid here in MA, half to low fan speed can get to 37 WOW!!! and at full fan, ~48-52 or so......so, I guess it is working fine, it certainly cools at least 15-20 degrees cooler than starting ambeint temp, I think it was ~82 inside this morning and very humid. Do you have any info on how the recirc functions...I noticed a little bump noise, then the air got warmer for just a second then cooled off quickly? I guess if there is not a problem as long as the recirc button stays on...IS there a way to feel if the recirc is sucking air from the bottom of the dash or anything? I guess everythign is fine, but just wondering how it works...sure was cold this morning :D . Let me know, thanks again, later, :D:):chevy:

biochemist Enthusiast

biochemist

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Hi...whoops! The ambient temp is the temp inside the cab, right?...I have been measuring the outside temp...so, my cab was 100+ (measured) today and within 1 minute the AC was blowing 58-60 deg. air...pretty good. Within 3-5 minutes down to ~54...seemed to settle at full+recirc at 52-55 degree...outside temp was 87 with 90% humidity...again, half fan gave ~44 degree air...Cab got to ~61 degrees in about 20 minutes or so, saw 37 !! this morning at lw fan speed...pretty good :D . Thanks, later, :D:):chevy:

biochemist Enthusiast

biochemist

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OK, so I about froze this morning again ~80 outside very humid...I think I get how it works...can get the cab to 57 degrees at half fan @60 setting...really cold air comes out then as low as 34 degrees (yes 34)...started condensing water on the outside of the truck actually...normal driving at full fan and recirc is ~50 degree air...anyway, I think I get how it works...seems to be able to regulate intermediate temps well also...63...it actualy will equilibrate the cab to 63...awsome, at lower fan speeds it is actaully so cold it feels uncomfortable if you have a body part next to a vent (like my knee)...anyway, thanks, later, :D:):cheers:

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