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  #1  
Old 11-05-2007, 12:10 PM
Matt
 
Join Date: Nov 2007
Location: Derby, CT
Posts: 40
I want warm

ok, someone help me with 1985 300sd.

I have had three mercedes benz from 1981 300sd, and 1983 380sl, and this one.

I can never get warm from my climate control, it's either to hot or to cold.

I'm not sure where to start my diagnosis.

Is it the mono-valve, cabin temp sensor, something else, a relay. the climate control unit.

i ALSO HAVE BEEN GETTING THIS BURNING PLASTIC SMELL FROM THE HEAT, NOT ALL THE TIME, ALL WHEN I'M TRYING TO GET WARM.

p.S. i NOTICED SOME KIND OF WIRING THAT HAS BEN SPLICED INTO THE WIRES ON THE PASSENGER SIDE ENGINE COMPARTMENT, NEAR STRUT HOLE. AND IT TRAVELS TO MY DASHBOARD, I HAVEN'T INVESTIGATED YET. sOME MORON BYPASSED SOMETHING. tHIS MIGHT BE RELATED MIGHT NOT. MAYBE THAT'S WHY I'M SMELLING SOMETHING.

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  #2  
Old 11-05-2007, 12:17 PM
83 300sd
 
Join Date: Sep 2007
Location: Dirty Jersey
Posts: 16
Probably not the mono valve since you do get cold try a climate module resolder.
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  #3  
Old 11-05-2007, 02:16 PM
Matt
 
Join Date: Nov 2007
Location: Derby, CT
Posts: 40
what tells controlls the temp of the heater?
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  #4  
Old 11-05-2007, 04:40 PM
Banned
 
Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
If the cabin temperature is fluctuating wildly, the cabin temperature sensor is the most likely culprit. It lives behind the small grate in the overhead panel.

If the sensor checks out, the CCU is the culprit..........but less likely if all other functions work.
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  #5  
Old 11-05-2007, 04:53 PM
toomany MBZ's Avatar
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Quote:
Originally Posted by DrFrizog View Post

i ALSO HAVE BEEN GETTING THIS BURNING PLASTIC SMELL FROM THE HEAT, NOT ALL THE TIME, ALL WHEN I'M TRYING TO GET WARM.

p.S. i NOTICED SOME KIND OF WIRING THAT HAS BEN SPLICED INTO THE WIRES ON THE PASSENGER SIDE ENGINE COMPARTMENT, NEAR STRUT HOLE. AND IT TRAVELS TO MY DASHBOARD, I HAVEN'T INVESTIGATED YET. sOME MORON BYPASSED SOMETHING. tHIS MIGHT BE RELATED MIGHT NOT. MAYBE THAT'S WHY I'M SMELLING SOMETHING.
On my '83, there is a number of electrical lines in the vicinity. Many bundled, so it will difficult to nail down. Do you note any melting insulation there?
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  #6  
Old 11-06-2007, 10:14 AM
Matt
 
Join Date: Nov 2007
Location: Derby, CT
Posts: 40
i only smell it when i set it to 22c. not when it's full blast heat. Haven't tried cold. i'm sure my ac is charged, but i just got it and it's cold outside.
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  #7  
Old 11-06-2007, 10:15 AM
Matt
 
Join Date: Nov 2007
Location: Derby, CT
Posts: 40
i did the paper test to the sensor and it holds it, so that works, so the only things that control warm are the sensor and ccu unit?
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  #8  
Old 11-06-2007, 10:28 AM
Banned
 
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Location: Blue Point, NY
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Quote:
Originally Posted by DrFrizog View Post
i did the paper test to the sensor and it holds it, so that works, so the only things that control warm are the sensor and ccu unit?
The paper test determines whether airflow is crossing the sensor. It's got nothing to do with whether the sensor resistance levels are proper at specific temperatures.
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  #9  
Old 11-07-2007, 09:14 AM
Matt
 
Join Date: Nov 2007
Location: Derby, CT
Posts: 40
well i get warm, but now i have to figure out what is burning, it's almost smells like a circuit board frying. But i'm not sure, it just strange that it doesn't happen when it's hot.
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  #10  
Old 11-07-2007, 09:20 AM
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Location: Golden Valley, AZ
Posts: 887
Maybe your blower is going south and pulling too many amps. I just had a bad blower destroy the CCU and the Sensor(I think). The sensor burned up after the blower was taken out. This is on a 126 gasser though.
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  #11  
Old 11-13-2007, 03:44 PM
Matt
 
Join Date: Nov 2007
Location: Derby, CT
Posts: 40
well, i'm going to open up the ccu to resoldered the joints, i'll look to see if anything melted.
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  #12  
Old 11-13-2007, 03:51 PM
Craig
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Just be aware that re-soldering the CCU will make it worthless as a core, so when you give up and buy a rebuilt one you will have to find an unmolested unit to trade in.
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  #13  
Old 11-13-2007, 03:56 PM
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Join Date: Sep 2007
Posts: 24
I had trouble with temp in my 85

I had trouble regulating the temp in my 85 300DT. I found that the foam tube that runs behind the glove box from the little vent on top of the dash to the temp sensor was gone. I simply connected the hoses that were left behind with a length of hose and now I have temp regulation.

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