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#1: 01-01-2005, 09:20 PM
How The Dual-Zone Climate Control Works
 
 c_hunter
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The ACC system has three basic modes:


1) Automatic When you push the auto button, the systems does whatever it can to adjust the cabin temperature to meet the temperature(s) set by the user. In this mode, the only user controls are the L/R temperature knobs. In theory, you should be able to adjust the "comfort" level by tweaking the temperature knobs at any time -- if it gets too hot, drop the temp; if it gets too cold, increase the temp. Note that the operation of the system depends on the temperature difference between the current temperature and the desired temperature(s). With large differences, the fan will run at higher speeds and the system will choose more agressive venting modes. With small differences, the system will react to temperature inputs very gently.

2) Partial override From automatic mode, any control tweaked by the user other than the temperature control -- ie, fan speed, mode, AC on/off -- will force the system into a semi-automatic mode. In this mode, the system will continue to try and reach the set temperature(s) using whatever remaining options the user has not overridden. This is often confusing, and it may seem that the ACC system is posessed, as it appears to change something else every time you tweak a control. In reality, the system is just trying to reach or maintain the set temperatures with fewer and fewer ways to do it.

3) Manual If the user has tweaked all possible controls, the system will eventually be in full manual mode. Here, the user has complete control over the entire climate control system. In this mode, the temperature scale no longer relates to absolute temperatures in degrees. Rather, the range of 65-85 degrees maps to a general temperature scale from LOW to HIGH. Note that 65=LOW corresponds to no heat added (thus max cold) while 85=HIGH corresponds to the most heat added (max warm).


To get into manual mode on purpose, the best thing to do is press OFF, and then bring the system back online by pushing the mode, fan, or AC buttons. You may then tweak any of these settings as desired and the system will remain in full manual mode from there on out. This is more or less equivalent to a regular manual climate control system, except you have a fancy LED display!

Note that you can invoke a no-fan vent mode by starting from OFF, and then pushing the mode button to select face or bi-level ventilation. In this vent mode, the temperature display will not show and the temperature will remain at the previously set level (before OFF was pushed). So if you want a totally ambient vent, the procedure would be to set the dial to 65 (no heat), press OFF, and then press mode to select vent. Pretty complicated, eh? ACC systems don't have simple direct controls for something like this, unfortunately.

One thing that seems to bother people is that air conditioning (AC) runs almost all the time in AUTO mode. Well sort of. The AC compressor has a clutch, and it actually cycles on and off as needed (cars have been doing this for years). It cools the air in warm weather, and dehumidifies the air in cool weather (or when defrost is activated). All the while, the AC indicator remains lit. This simply indicates that AC can come on if needed, even though it may not be on full time. In extremely cold weather, the AC indicator will stay off until the engine warms up because it is too cold for the compressor to run. Once the engine warms up or the ambient temperature increases, the AC indicator may come on, again, to indicate that AC can activate if needed.

Another thing that bothers people is the fact that there is a world of difference between the temperature setting of 65 and 66. As discussed above, 65=LOW, or no heat added. So while 66 indicates a set temp of 66F in AUTO mode and it's the lowest setting for heat in the manual mode, 65 indicates "no heat". In AUTO mode, 65 actually translates to maximum cool (try it in the summer, it will frost your tootsies off). I really think Subaru should have labeled 65 as "LOW" (and 85 as "HIGH") similar to Acura.

Finally, many people complain that the system gets too hot or too cold while honing in to the set temperature in automatic mode. The solution for this is rather simple -- just reach over and turn the temperature knob(s) in the direction that will make you more comfortable. For instance, if you set the system to 75 in the winter and it's getting too warm, try cranking it down a few notches until you see the fan speed drop a level or two. What you are doing is telling the system "whoa" without having to fight with it; this really amounts to an impromptu calibration.

I hope this helps and saves people some grief. And for those of you who don't like the ACC at all, I respect your opinion -- I am just trying to alleviate some of the confusion that has been going around. I do agree that the system has flaws and eccentricities, and could be improved.

Craig

Last edited by c_hunter; 01-02-2005 at 08:11 AM..
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