How The Dual-Zone Climate Control Works

I wanted to take the time to post an update on my experiments fixing the climate control system. My experience after a year and one half is that the system works fairly well in warm weather but pumps out far to much heat, even on the lowest setting, in cold weather. The problem is insufficient airflow over the temperature sensor. The temperature sensor is located right behind the lower dashboard fascia. The port is the pair of horizontal slits in the dash right next to the driver's right knee, just to the left of the radio. To access the sensor you need to remove the lower black panel under the driver's side dashboard, the lower dash panel under the steering wheel column, the shifter boot and cover, the piece of fake wood trim to the left of the shifter and the fascia piece along the forward driver's side of the center console. The sensor itself is inside of a rectangular black housing. Connected to the rear of the housing is a light gray flexible plastic conduit which travels deep up into the dash and connects to the HVAC system. Air is drawn through the conduit and over the sensor by a venturi (i.e. air flow through the system sucks air through the conduit). The problem is insufficient airflow. I met with Sam and bought the parts he uses in his Forrester fix. The link to find Sam is here:

 

http://www.geocities.com/samiam_68/SubaruCCS/SSC_Fix.htm

 

The big difference between the Forrester and the LGT is that you cannot simply disconnect the upper end of the conduit and plug it into the fan. The upper end of the LGT conduit is buried way the hell up into the dash where no human can possibly wriggle his hand. My solution was to disconnect the existing conduit at the sensor housing and connect a one foot piece of new flexible plastic conduit to the housing, route the conduit to a location just to the left and below the steering column and locate the fan there. The fan is mounted to a metal piece of the inner dashboard structure which detaches by removal of two screws.

 

Once re-assembled the system works beatifully but I found the fan noisey. After living with the fix for the past month I removed it two days ago to see if I could find a solution for the noise. I have been corresponding with Sam and he suggests perhaps a quieter fan with a lower cfm rating. The assembly which Sam supplied me with uses a Sunon KDE1204PFVX which is rated at cfm 8.6. My thoughts are either a less aggressive fan or maybe the addition of volume control, rheostat or potentiometer (you have to cut me some slack here since I'm not well versed in electronics). I rather prefer this since it gives you the option of controlling the fan speed. I'm just not sure yet where I will locate the control.

 

In the meantime I drove the car this morning and as I was waiting for the sensor to come up to temperature I had an idea. I turned the fan on high. This is somewhat counter-intuitive. If you are sitting in an uncomfortably hot car the last thing you want to do is blast the fan on high. But it worked, within five minutes the sensor regulated the heat to a comfortable level. It worked because I increased airflow over the sensor. As soon as the sensor came up to temperature the system immediately switched from footlevel airflow to bi-level airflow and at that point I simply hit the auto button, the fan speed lowered and the system maintained a comfortable level.

 

Now mind you, I still intend to pursue re-installing the fan with a fan speed control to make the system work automatically as it was intended to. But for those of you unwilling to go through the time and effort of installing the fan I suggest you try cranking up the fan when you first jump in the car in the morning and leaving it there until the bi-level kicks in. If I get this all sorted out I will try to post some pictures.

I wanted to take the time to post an update on my experiments fixing the climate control system. .

 

GREAT STUFF! This has been a frustration for me for 2 winters. Never thought about putting it on high to draw more air through the venturi--good thinking.

Definitely keep me up to date on your fan idea--would love pics and part details as I definitely would like to do this.

 

I haven't pulled off the panel yet, but what about just "blowing" some more air in the 2 slots on the panel by your knee?

Originally Posted by Mike M http://legacygt.com/forums/skynetim/buttons/viewpost.gif

I wanted to take the time to post an update on my experiments fixing the climate control system.

 

 

Thanks for your effort to improve our bad-acting ACC units. I'm not sure I follow you so I have a couple of questions.

 

1. Did installing the additional parts increase the airflow enough to work correctly? I ask because you also say you had to turn the fan on high to get it to work correctly.

 

2. What caused the increase in fan noise? Is there no fix for that other than replacing the fan with a quieter one?

Caramall2,

 

To answer your question it is possible to blow air in through the vents but that would require mounting a fan assembly on the outside of the dash (rather aesthetically unpleasing) or mounting a fan sandwiched between the dashboard fascia and the sensor housing. This would require modifying or cutting the housing and possibly epoxying a small 40 X 40 X 10 fan to the housing itself. This is an intriguing idea. The possible downside is that the fan would be mounted very close to the front of the dash and its operation might be even more audible than if it were buried deeper behind the dashboard.

 

lgt_nube,

 

It think you are confusing my comments on the installation and operation of Sam's fan assembly with my comments on the operation of the LGT's HVAC fan. Sam's fan assembly (which functions merely to draw cabin air across the sensor) works flawlessly once installed but I found it's operation somewhat noisey for my taste. The solution would seem to be a quiter, lower flow fan or a potentiometer with which to adjust the fan speed. As an alternative to installing Sam's fan try simply cranking the LGT's system fan up on high to get the sensor quickly up to cabin temperature.

Actually I did the Ram Air modification months ago. I used a 18 volt fan and its much quieter, then I relocated the sensor and located the fan just inside of the outer panel. The install went well and it does a nice job forcing the intake air into the sensor.

 

I have news for you, thats not the only problem with the system.

On a cold morning say 20 degrees outside with the settings both set to 70 degrees the system goes into heat mode and pumps the car to 76. Then the A/C turns on to bring the car back to the set level. It tapers down near 72 and will hold true within reason. If during this time you set the controls to 66 instead of 70 the car heats up to 72 then tapers back into a more comfortable setting. If at anytime you turn it down from 66 to 65 you automatically get A/C down to 63 degrees cabin and then gradually floats up to 65.

 

In essence this is still the WORST Heat - A/C system I have had in any of the over 30 new cars I have purchased.

Darn good thing this car works well in the snow or it would be in someone elses garage.

 

If you have any questions please feel free to ask. I have invested over 11 hours inside this dash and have the scars to prove it.

Mike S

Audioi,

 

I am very interested in your installation. Can you give us some information on the fan (i.e. size, cfm rating, the make and model number). It sounds like you have the fan sandwiched between the outer panel and the sensor housing. Do you have any pictures or if not can you give us a more complete description?

 

I found that once I had Sam's fan assembly installed, simply leaving it set between 66 and 68 (66 if I'm alone or 68 if my wife who demands a warmer car is with me) kept the temperature within a comfortable range.

lgt_nube,

 

It think you are confusing my comments on the installation and operation of Sam's fan assembly with my comments on the operation of the LGT's HVAC fan. Sam's fan assembly (which functions merely to draw cabin air across the sensor) works flawlessly once installed but I found it's operation somewhat noisey for my taste. The solution would seem to be a quiter, lower flow fan or a potentiometer with which to adjust the fan speed. As an alternative to installing Sam's fan try simply cranking the LGT's system fan up on high to get the sensor quickly up to cabin temperature.

Thanks. I missed the point that Sam's parts included a fan assembly.

Do "we" know which model years have this very strange-working ACC unit. Mine's a 2005 LGT Limited and that's the only year I remember seeing in this thread (but I haven't really checked).

I have a 2006. I believe the systems are the same as the 2005.

Mine is a 2007 LTD OBW and the mod didnt really help.

A+

Nice explanation, thanks! That AC on when Auto mode is on bugged me. Thanks for clearing it up.

I love my car, but I wish the Clim. control was as good as my old A4's...

I think those Japanese engineers had way too much sake when they designed that climate control. Actually, it's more like they got carried away with all the things that computer control made it possible to do and they did all of them, regardless of if most of those things made any sense. The whole thing is a bad joke and one that Subaru seems oblivious to or they would have fixed it after one bad year.

I have since given this car to my wife and purchased a new Audi and I was almost getting used to the quirky crappy climate control until now.

This is a issue they really need to correct.

What is the issue? I find it very easy to operate -- I leave it at 69 in the winter, 74 in the summer other than needing to activate the windshield defogger and it works great.

Biggest issue to me is (I have a 2005), if you're just driving 15 minutes to work in the winter, the sensor never heats up enough to move the damper from full heat. So...if you set it to 65 freezing air comes in (because 65 is full "cold" air), if you set it to 66, you roast (because sensor thinks it's too cold and it's full "hot" air). So on my way to work I have to flip back and forth between 65 and 66...just not something I planned to do on a $30k+ car (smile). I drove a non-GT the other day with the plain old controls and it was great to just set the "cold/hot" damper right where I wanted it.

 

This has been a problem on other Subarus too from what I've read. The sensor just doesn't get the proper flow to accurately sense the cabin temp until you've been in the car for 20 minutes or so.

...you need to remove the shifter boot and cover, the piece of fake wood trim to the left of the shifter and the fascia piece along the forward driver's side of the center console.

 

Does anyone have any interior part diagrams or photos of this? I am not sure where the retainer clips are and would like to remove these parts. The fake wood trim pieces that run along the side of the console...and the shifter panel to install a custom boot.

 

I want to paint the fake cherry wood plastic pieces as well. Looks like it can easily break when trying to remove from the retainer clips.

How can I keep in "auto mode" and not have airflow only from the dash registers? I want to use the auto function and have the airflow split between the defrost and footwell registers. My system always routes airflow to the dash registers/vents only in "auto" mode and reverts to manual whenever I redirect airflow to bi-level or even split between footwell and defog registers/ vents.

The system remains in auto mode for all functions except the ones you set manually. Yes, the Auto light disappears but it's still in "auto mode" for all the other functions when you set the airflow to another setting.

 

My issue with that split airflow mode (defrost and footwell) is that the air temperature in the two directions is not the same. The footwell air temp will be warm and the air going to the windshield will be cold (or cool) which is silly for trying to keep the windshield from fogging. Just another bad design item.

 

How can I keep in "auto mode" and not have airflow only from the dash registers? I want to use the auto function and have the airflow split between the defrost and footwell registers. My system always routes airflow to the dash registers/vents only in "auto" mode and reverts to manual whenever I redirect airflow to bi-level or even split between footwell and defog registers/ vents.

I test drove and put a deposit on an '05 LGT that I hope to pick up by the end of the week. When checking to make sure everything worked I looked at the climate controls, pushed a few buttons and was completely lost within seconds, lol. I just took note that everything seemed OK with it and said to myself "I'll figure this nonsense out later". I'm used to economy cars with manual controls and Jeeps with zip up windows, this near luxury stuff is beyond me

Like I've said, nice car but it would be a better ride if you could downgrade to the manual temp control or stuff anyone else's climate control in it.

My wife said its best to regulate it with the windows.

 

They REALLY need to correct this!

In the morning I give my car ten minutes to warm up, 5 minutes to cool down and another minute to equalize.

This post answered a bunch of my questions. The most helpful was the explanation on the A/C light. I keep telling myself to read the manual, but I don't get that much time to just sit parked in the car. Taking the manual out of the car is out of the question of course.

 

-Ben

silly question but here I go. If I have a "Normal" heating unit with the single CD, can I swap out for the Duel Climate and 6disk? Is it something that I do not want to toutch or should I just wait until I trade in and buy a beter Legacy.