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  #1  
Old 01-15-2007, 08:20 PM
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Possible overcooling and unreliable heat

Here is the problem that I seem to have. First off my temperature gauge only reads about 60C. I believe it is related to another problem which I have been having. Sometimes when I start my car from a cold start, I have to drive it for 10-15 minutes until it gets up to operating temp. and then turn the car off, and restart it before the heat will kick in. Otherwise the heat is just moderate.
I had just done some maintenance on my car over the break, so I decided to give it an italian tune-up on the way back. At this point the temp. gauge was still reading at about 60C, and the heat was on full blast. After I got the car to about 3700 RPM, the heat cut off and cool air began to blow from the vents. So I stopped the car, turned it back on, and the heat was fine again. This happened one more time later in my trip, when I got the car up to about 85 MPH.
From what I read, this is most likely a fualty T-stat. What else might be causing this?

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1983 300D Turbodiesel
1976 300D Rustdiesel
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Old 01-15-2007, 08:32 PM
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Which car are we talking about ?
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Old 01-15-2007, 08:35 PM
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Sounds like maybe two issues......

Check/change thermostat first (for eng. temp 60C)

Check/rebuild monovalve (for heater)................or this may also be cracked solder joints in the ACC pushbutton controller.
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Last edited by SD Blue; 01-15-2007 at 08:45 PM.
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Old 01-15-2007, 08:36 PM
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Quote:
Originally Posted by log673 View Post
From what I read, this is most likely a fualty T-stat. What else might be causing this?
That's your issue. You'll never get decent heat at an engine temperature of 60C.
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Old 01-15-2007, 08:43 PM
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Quote:
Originally Posted by log673 View Post
the heat cut off and cool air began to blow from the vents. So I stopped the car, turned it back on, and the heat was fine again. This happened one more time later in my trip, when I got the car up to about 85 MPH.
You could have three problems...what the others have suggested PLUS an issue with the ACC controls..... my 81 wagon only took me punching the buttons on the dash as ' Suggestions' .... it might respond then...or 15 minutes from then.... or sometimes never...
and I know from other posts that I am not the only one who has experienced " HAL" taking over the dash panel.... so you may have ACC and or pod flap control problems also.. which are very hard to deal with because they are usually intermittant...
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Old 01-15-2007, 09:46 PM
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Quote:
Originally Posted by leathermang View Post
You could have three problems...what the others have suggested PLUS an issue with the ACC controls..... my 81 wagon only took me punching the buttons on the dash as ' Suggestions' .... it might respond then...or 15 minutes from then.... or sometimes never...
and I know from other posts that I am not the only one who has experienced " HAL" taking over the dash panel.... so you may have ACC and or pod flap control problems also.. which are very hard to deal with because they are usually intermittant...
I was already pretty sure that HAL was not opening the pod bay doors on my ACC when I bought the car, but I didn't really see it as that big of an issue since the heat generally worked fine. I don't use the A/C much anyway. I'll work on that if it gets too hot this summer. I'll try replacing the T-stat this weekend and see what happens. And this is my 1983 300D.
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1983 300D Turbodiesel
1976 300D Rustdiesel
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  #7  
Old 01-15-2007, 09:51 PM
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Mercedes uses ACC to mean Automatic Climate Control.... which includes all the fresh air vent, heating and AC..... there are three types... all with there own large and complicated sections in the Factory Shop manual....
You do need to replace the Tstat first....
but then we will need to know which car you are talking about as they have different ACC types...
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  #8  
Old 03-02-2007, 10:23 PM
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I pity the fool...
 
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Location: Memphis, TN
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I finally got around to flushing my cooling system and replacing the T-stat. That fixed the overcooling problem, but I still cannot get heat all the time. Sometimes it is great, but other times it is just lukewarm. Is the monovalve at fault? And is there anything I should check before replacing that?

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"There are a lot of pebbles on the beach, but there's a Little Rock in Arkansas."

Logan

1983 300D Turbodiesel
1976 300D Rustdiesel

Last edited by log673; 03-02-2007 at 10:55 PM.
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