# Interesting AC phenomenon - not a vital or critical issue



## Eco (May 13, 2011)

I'm going to first start off by saying this likely is designed to do this, something to do with the variable compressor or something but I found it to be odd.

OK, next time you're driving your car around, make sure the radio is off so you can listen for changes in air volume from your HVAC.

Turn your AC on, (I cannot remember if it's when the car is on recirculate or not, or both - so please try various combinations)

Edit: *Then Turn your fan speed to it's highest setting and then drive around*

What you'll likely observe.
For some reason I believe it's boost related and not RPM related, when you get into boost you'll notice the physical volume of air, or fan speed will actually drop, the HVAC system will reduce in vigor, as soon as you let off the gas, it ramps back up again.

It drives me nuts because in stop and go traffic its like someone constantly changing you from a NORMAL CAR's setting 4, to 3, to 4, to 3 LOL.
Has anyone else observed this?

One last complaint.
Has anyone in the world noticed or wondered why the HVAC fan system settings feel like this. (Percentage of total capacity)

Setting 1: 10% Setting 2: 25% Setting 3: 35% setting 4: 100%

It's like what the heck GM, nothing b/t 35% and 100%!? It either goes from, not adequate, to WHOA WAAAAY too much! Haha.


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## spacedout (Dec 7, 2010)

Eco said:


> One last complaint.
> Has anyone in the world noticed or wondered why the HVAC fan system settings feel like this. (Percentage of total capacity)
> 
> Setting 1: 10% Setting 2: 25% Setting 3: 35% setting 4: 100%
> ...


Completely agree & actually think you have the percentages exactly what I would say it feels like.


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## silverls (Nov 12, 2011)

It has to do with rpms not boost. My 1.8 does this as well and so have most of my previous vehicles. I believe the basics revolve around cutting back on the a/c when the motor is under strain or when the rpms drop to low. Don't know all the technical crap for this one

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## Eco (May 13, 2011)

Oh it is RPM? I'll have to check that out, since I didn't recall it only happening at idle versus driving. In fact I'm almost certain it has to do with throttle input, it may ALSO happen at RPM, but for instance, If I'm in a neighborhood driving 20 mph in say 3rd gear, getting on and off the throttle might literally only change the rpm by say 50 within a second or so but the second I get back on the throttle the volume drops.

This HVAC fan also likes to chirp on settings from 1-3. It takes a little while for it to run, I wish I could access it to spray some RP lube on it or something.


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## rustinn (Jun 7, 2012)

I believe it's designed to do this to prioritize power (when you need it) over fan speed.


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## Eco (May 13, 2011)

I'm just confused, because it's an electric squirrel cage fan. You have MORE power on tap when in the throttle, and LESS off, so that isn't a plausible explanation.


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## silverls (Nov 12, 2011)

Eco said:


> I'm just confused, because it's an electric squirrel cage fan. You have MORE power on tap when in the throttle, and LESS off, so that isn't a plausible explanation.


I didnt explain well but its not about boost because it happens on non turbo cars. It has to do with Rpms in a sense that the higher rpm ur at, the more power the car needs. So it will cut down on accessories that use power to "prioritize" as above put it and put power where you car needs it.

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## Dale_K (Jul 16, 2011)

I'm pretty sure it's related to how the car runs the alternator and charges the battery. Try turning on your DIC display to the volts page while trying your experiments. The car attempts to charge the battery as much as possible while you're coasting. So when you're on the power the computer tells the alternator to stop charging and the system voltage is reduced. The fan will go slower with less volts. Then when you lift off the gas pedal the car will try to charge the battery and the system voltage will go up and the fan speed will increase. It's a fuel economy strategy. If your battery starts to get weak the car detects it and tells the alternator to charge it regardless of whether you're coasting or not, so the funny fuel economy mode won't make your battery go dead.


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## jblackburn (Apr 14, 2012)

^this.


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## Bohdan (Apr 28, 2012)

It is completly different on the LTZ versions. Fan speed 4=50% 5=70% 6=100%.


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## 70AARCUDA (Nov 14, 2010)

...search on GM's Regulated Voltage Control (RVC) System here, there are quite a few postings on this device and it's effects.


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## jblackburn (Apr 14, 2012)

Bohdan said:


> It is completly different on the LTZ versions. Fan speed 4=50% 5=70% 6=100%.


I wish. I don't know who designed the fan speeds on the cars with settings 1-4, but they're stupid.

Shutting vents gets you a lot more tolerable airflow on setting 3...unless you have a passenger or people in the back seat that want air. Then it's still useless and it's back to tornado mode.


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## Eco (May 13, 2011)

Lol tornado mode! Hahaha.


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## mcg75 (Mar 5, 2012)

I find the system works pretty good actually. 

#3 is great when you have the airflow directed to one spot whether it's windshield, dash or floor. 

#4 is great when you have the airflow split between any two of windshield, dash or floor.


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## Patman (May 7, 2011)

Eco said:


> I'm going to first start off by saying this likely is designed to do this, something to do with the variable compressor or something but I found it to be odd.
> 
> OK, next time you're driving your car around, make sure the radio is off so you can listen for changes in air volume from your HVAC.
> 
> ...


I think that may be what I took my car back to the dealer for. Complaining that the fan was too strong. FYI nothing was found wrong with my AC at the dealer. Today I noticed it was much better(not as strong) driving a lot on the highway on outside air.


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## blk88verde (Apr 30, 2011)

I did notice my a/c would stop blowing cold when the engine is under a heavy load climbing long hills. Once I let up and started down hill the air got super cold. I suspect with our little engine, GM programmed the a/c to reduce load on the engine when power is needed.


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## gregh2000 (Oct 13, 2011)

I also learned something important about the ac the other day. The dealer had one of those inspection papers on the seat when I picked it up, I put the paper in the glove box and started the car. Once I started to drive I heard this vwooop and the ac power was cut down big time. If I put it to outside air it was strong but recirc it was weak. I could hear something buzzing. I found out by taking the glovebox out and down it sucked the paper into the intake. So the intake for the recirc is behind the glovebox so if you put too much in the glovebox it will suck it in. Who designed this car?


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## NBrehm (Jun 27, 2011)

gregh2000 said:


> Who designed this car?


Koreans


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## 70AARCUDA (Nov 14, 2010)

gregh2000 said:


> Who designed this car?


...FYI, _our_ 2011-2012-2013 GM "Cruze" actually began life as a 2008 *Daewoo* (South Korea) *Lacetti Premiere*.


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## Eco (May 13, 2011)

gregh2000 said:


> I also learned something important about the ac the other day. The dealer had one of those inspection papers on the seat when I picked it up, I put the paper in the glove box and started the car. Once I started to drive I heard this vwooop and the ac power was cut down big time. If I put it to outside air it was strong but recirc it was weak. I could hear something buzzing. I found out by taking the glovebox out and down it sucked the paper into the intake. So the intake for the recirc is behind the glovebox so if you put too much in the glovebox it will suck it in. Who designed this car?


http://i263.photobucket.com/albums/ii129/irishlass3375/intredasting.jpg


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