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How The Dual-Zone Climate Control Works


c_hunter

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  • 3 weeks later...
  • 3 months later...

Hello,

 

I see several people here have the same problem I have. 65 is NOT max AC if you are in defrost (blowing on the windshield) mode. In defrost, the compressor comes on, but the air comes in at what feels like about 70 degrees, which can be pretty warm if you've been backpacking in the cold... Heavy breathing, warm breath, means lots of fog, so I turn on the defrost, and get baked. I have to turn the defrost on full and open the windows, or blast my feet with freezing air if I turn to defrost+feet mode. If my shoes are all muddy from backpacking, I'll take them off and drive barefoot to dry off my feet...

 

What a pain. I just want defrost with cold AC. :p

 

Joel

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Hello,

 

jp928, yeah I got that... but what if I don't need max defrost? What if I need cool air, warmer than outside, but not hot, while still being dry, so that I can drive a couple hundred miles without fog on my windshield? :p

 

I just hate when marketing think they're being smarter than the consumer and they make things better by getting rid of choices that have existed for decades.

 

Ahh well... it's not like people take AWD Subaru Outbacks in the cold or anything, eh?

 

Joel

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Shouldnt have bought something with climate control, where somebody else decided the parameters.

What, I cant buy this car without climate control? Mmmmm, well, time to balance up the good bits and the bad bits.....So many things fall into this area now, you just have to get used to it, or stick with something older and simpler, until it falls to pieces. Now with the ergonomic problems raised in these forums, one has a better argument that ought to be forcibly put to Subaru, as they dont relate to emissions or safety as such, just plain common sense.

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Hello,

 

jp928, there's a better option. The same option that centerpunch, jazzymt, and others have come up with for the lack of a line-level input into the OE stereo: if enough people don't like the way it works, someone with the right know-how can create a fix that anyone interested in can then apply. I think it's great to discuss the major weaknesses of these systems so that fixes can eventually be made.

 

I have jazzymt's input board and am installing it this weekend. For $35, I resolved a major complaint I had about a nearly $30k car!

 

Now, if someone can give me cold air AC and not just the AC compressor on Defrost for $35, WOOT WOO! I'm interested...

 

Joel

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What about just getting fresh air through the vents with no heating or cooling? There are times when it's cool enough to go A/C-free but cracking the windows open isn't an option to keep the cabin temperature at a comfortable level. I tried manually adjusting the system but all I got was warm air through the dash vents.
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I think I answered my own question this morning about just getting fresh air from outside.

 

Turned on the auto climate control, set the dials to 65 and turned the AC button off. Setting the dials to 65 seemed to do the trick. It felt as though I was getting fresh as opposed to refrigerated air.

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  • 3 weeks later...

Well some more information for this active thread. Thanks for starting it Craig. I have a new 2006 GT.

 

When the AC light is on, no matter what mode, the air conditioning compressor clutch is engaged and compressor is doing its thing - compressing the freon-replacing CFC so it is ready to expand and cool down air flow. With the AC light still on the clutch will cycle on and off to maintain the correct CFC pressure for this cooling operation. It doesn't need to and actually doesn't run full time to keep the CFC pressure at the correct level. It does run most of the time and the amount is dependent on the cooling effect needed related to variables such as ambient temperature, solar load, etc. You can watch the clutch cycle on and off as needed.

 

My statement is supported by my observations of my new car as well. You can watch the clutch engage and disengage and it's behaviour in various modes by simply lifting the hood and watching the clutch on the front of th AC compressor. It is easily visible without removing any engine covers and with the window open you can even hear it from the drivers seat after a little practice.

 

Engaging or disengaing the clutch blips the engine rpm very slightly as well and this is discernable. This rpm blip signifies the additional load required to drive this compression process. From memory this loss is not trivial equating to 5-10 horsepower parasitic loss and a resultant loss in fuel efficiency and mpg.

 

The AC light and AC compressor come on at many inappropriate times not only the times necessary such as cabin cooling with a high outside temp or when defrosting. This is an unnecessary power loss and fuel loss. I have voiced my opinion to my dealer to no avail. Just some bad software design decisions and poor usablitity testing.

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Well after living with my LGT for almost a week, I have to agree with danbart and c_hunter. The major problem with the system is that it is scaled wrong. A range of 65 to 85 (in reality 66 to 84) does not allow enough adjustment on the bottom end. A more proper range might be 60 to 80 (in reality 61 to 79). There are mornings where I only want enough warmth to take the edge off of the the air flowing in and it's jut not possible in the current setup. It seems to me that this should be fixable by tweaking the programming or system code. Anybody out there with the knowledge or resources to do this?
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Mike, it may be possible to rescale the temp sensors if we knew where they were and which ones did what. They are likely thermocouples that convert a temperature into a voltage. You can always play games with sensors like that. The trick would be figuring out how the system worked and how the sensors feed into the controller, etc. If somebody can get a circuit diagram, that would be a good start.

 

Craig

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Craig,

 

That's interesting. I guess it can be approached either from an electrical engineering point of view or a software programming point of view. Does the climate control system have its own chip or does the code lie within the ECU?

 

Mike

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I put a pocket probe thermometer in the dash vent and the temp got to 49 degrees. My buddies 97 Maxima with 97,000 miles cranked out 42 degree air. Wonder if the system needs to run a bit otherwise the system is still not up to snuff. The air temp coming out before the relay was fixed was 60 degrees with it on max cold (65/65 left it on recirc.
42 is pretty cold. Most cars put out around 50 degrees F.

 

My cold weather strategy is to shut the system off until the water temp gage has started to move. My thinking is that putting it on before that will call for heat and just increase the volume of cold fluid that has to be warmed up. Anyone ever test this theory?

Who Dares Wins

スバル

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42 is pretty cold. Most cars put out around 50 degrees F.

 

My cold weather strategy is to shut the system off until the water temp gage has started to move. My thinking is that putting it on before that will call for heat and just increase the volume of cold fluid that has to be warmed up. Anyone ever test this theory?

 

When you put it in Auto it does that for you. Starts at minimum and goes full balst as the coolant temperature goes up. That's the only nice thing about this ACC IMHO.

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Craig,

 

That's interesting. I guess it can be approached either from an electrical engineering point of view or a software programming point of view. Does the climate control system have its own chip or does the code lie within the ECU?

 

Mike

 

Good question -- I don't know. I suspect there's a controller box somewhere that only handles the climate control. ECUs are generally not "bothered" with this sort of stuff.

 

Craig

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  • 2 weeks later...
My AC seems to turn on by itself in manual mode -- it's winter and I have no need for the AC. Any way to prevent this?

 

It probably means you haven't really gotten into manual mode. From true manual, only pushing defrost or AC will turn it on. Anyways, once you turn it off, it should stay off.

 

And BTW, it's not necessarily running, as we discussed above. But I understand exactly what you're thinking -- when I go full manual in cold weather, I also turn off AC unless I am worried about humidity/fogging.

 

CRaig

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It probably means you haven't really gotten into manual mode. From true manual, only pushing defrost or AC will turn it on. Anyways, once you turn it off, it should stay off.

 

And BTW, it's not necessarily running, as we discussed above. But I understand exactly what you're thinking -- when I go full manual in cold weather, I also turn off AC unless I am worried about humidity/fogging.

 

CRaig

 

Hmmm, maybe. I'll check tomorrow. However, I am pretty sure it is not in auto mode. It does not say auto and I turn it onby using the flow control button.

 

Mark

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