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  #1  
Old 05-23-2009, 09:59 AM
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Climate Control Question/Problem

Hello everyone,

On my 83 300D, I have heat and AC, but no ability to vary the temperature in between. Also, when I turn on the defroster, it comes out as full heat even with the wheel set to the coldest setting. Any idea on how to remedy these issues? I'm almost scared to do anything, because I do get the extremes of each. Thanks!

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  #2  
Old 05-23-2009, 10:32 AM
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Quote:
Originally Posted by ksmmspt View Post
Hello everyone,

On my 83 300D, I have heat and AC, but no ability to vary the temperature in between. Also, when I turn on the defroster, it comes out as full heat even with the wheel set to the coldest setting. Any idea on how to remedy these issues? I'm almost scared to do anything, because I do get the extremes of each. Thanks!
You'll need to provide more details regarding "no ability to vary the temperature in between". Do you get full heat all the time...........or full cold all the time.............the more details about what it's doing will assist in a better diagnosis.

The defroster is designed to provide maximum heat and maximum blower speed and these two positions are unchangeable. Ask the Germans about that bit of logic. Effectively, the defrost position is only good for 30 seconds.
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  #3  
Old 05-23-2009, 10:43 AM
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Brian is correct as always, especially about the "wisdom" of only high heat on defrost. I guess the Germans are serious about defrosting!
You can blast the defrost to clear things up then go to the button right next to defrost [bi-level] to keep it defrosted yet have cool air. A little air escapes to the defrost vents at that setting.
I have the same issue as you as far as "all or nothing" on heat and AC. With the temp wheel all the way cold I have full AC, but if I dial it down at all off of that setting then I get heat. I imagine mine is a CCU issue as I'm guessing the monovalve is told to open.
Full AC is usually required anyway, so to turn it down I just go to the bi-level setting. Could also have something to do with temp sensor in dash. Not sure how well those work after 25 years, or how well they worked new for that matter.
At least congrats on having full AC when needed. That is the usual problem with these cars......
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'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
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Old 05-23-2009, 11:03 AM
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Jimmy L and Brian,
That's pretty much my issue in a nutshell. I do know that my hose to the dash sensor has desinigrated (sp) and I have yet to replace it. I don't know if that will make much of a difference as I was afraid you were going to say that the CCU was the culprit (probably). I either have high heat or full AC at each end of the wheel. I replaced the monovalve in the winter which helped the intermittant heat problem. I would just love to have a little less heat at times. My AC never gets too cold unless its raining due to the PO relacing the refrigerant to R134.

I guess my next question would be: If I replaced the CCU do you think that would allow varoius temperature settings to occur? I don't know what these cost, but I'm sure they are not cheap.
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Old 05-23-2009, 11:05 AM
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Jimmy L,
Thanks for the tip on the bilevel button. I'm not sure why the Germans thought that only heat was necessary for the defrost.
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  #6  
Old 05-23-2009, 11:07 AM
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You can get a good used CCU from somebody on here I imagine, or a rebuilt unit online for $250 or less. First thing you need to do is replace your disintegrated foam tubing under the dash and see if that does anything. Air is pulled over the sensor via that tube. It is doubtful they make much of a difference, but you need to at least rule it out....
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'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John
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Old 05-23-2009, 11:41 AM
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Quote:
Originally Posted by ksmmspt View Post
I'm not sure why the Germans thought that only heat was necessary for the defrost.
I believe that you have been misinformed. My information indicates that the "Defrost" mode should operate maximun heat, maximum blower speed and air conditioning.
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Old 05-23-2009, 11:43 AM
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Originally Posted by Brian Carlton View Post
Effectively, the defrost position is only good for 30 seconds.
Then what happens?
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Old 05-23-2009, 11:50 AM
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Originally Posted by tangofox007 View Post
I believe that you have been misinformed. My information indicates that the "Defrost" mode should operate maximun heat, maximum blower speed and air conditioning.
We were talking temperature Tango, and I guess weren't specific enough to also note that the compressor is turned on, removing the humidity. Duly noted....
The temperature of the air is still warm/hot, and that was ksmmspt's point.


Quote:
Originally Posted by tangofox007 View Post
Then what happens?
You get hot Tango. Quite the hair-splitter today, eh?
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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John
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  #10  
Old 05-23-2009, 11:57 AM
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Originally Posted by ksmmspt View Post
I guess my next question would be: If I replaced the CCU do you think that would allow varoius temperature settings to occur? I don't know what these cost, but I'm sure they are not cheap.

The CCU is the likely culprit when the temp wheel has no response and the monovalve is working properly. However, it's not a certainty if the vehicle temperature sensor isn't working properly.

A rebuilt CCU is about $200............or you can roll the dice on e-bay for about $60. I've done both, and the former is definitely more pleasurable.
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  #11  
Old 05-23-2009, 11:58 AM
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Originally Posted by tangofox007 View Post
Then what happens?
The internal body temperature rises to unsafe levels.
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  #12  
Old 05-23-2009, 11:22 PM
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Originally Posted by Brian Carlton View Post
The CCU is the likely culprit when the temp wheel has no response and the monovalve is working properly. However, it's not a certainty if the vehicle temperature sensor isn't working properly.

A rebuilt CCU is about $200............or you can roll the dice on e-bay for about $60. I've done both, and the former is definitely more pleasurable.

Ok. $200 or so is probably fair. Do you have a good reputable source for the rebuilt CCUs? Thanks.
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Old 05-23-2009, 11:40 PM
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Originally Posted by ksmmspt View Post
Ok. $200 or so is probably fair. Do you have a good reputable source for the rebuilt CCUs? Thanks.
Before you get too carried away throwing money at parts, be mindful of the fact that the CCU is primarily a switching device. The actual temperature control is accomplished by the temperature control unit. Which cannot function properly without good input from the temp sensor.

I would recommend that you repair the hose to the temp sensor before you spend any serious money.
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  #14  
Old 05-23-2009, 11:45 PM
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Originally Posted by ksmmspt View Post
Ok. $200 or so is probably fair. Do you have a good reputable source for the rebuilt CCUs? Thanks.
These fellows are reputable:

http://www.programainc.com/default.php

But, note the point made by TF before you just toss money at it.
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  #15  
Old 05-24-2009, 12:02 PM
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I was successful by taking the the unit out and repairing cold solders.

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