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  #1  
Old 05-24-2002, 01:27 AM
Mike Murrell's Avatar
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Question W126 - Cooler Vent Temps At Slow Vs. Highway Speed

Had local MB tech check low/high side pressure. Checks out. Getting 52 degree air at center vents at highway speed. If I exit the highway and drive around at say 25-35 mph, I soon see vent temps drop to 45 degrees.

Local tech indicated this could be the result of a long list. The car is 11 yrs. old and is equipped with orig. compressor, etc. - R12. Compressor seems to cycle often at highway speed. Suspected overcharging, but again, pressure check indicated all is well.

Serpentine belt is in good shape and properly adjusted.

I suspect an aging clutch and /or expansion valve.

Thoughts appreciated.
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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"
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Old 05-24-2002, 01:33 AM
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Mike:

My 300E has always done this but I never questioned it as I always assumed that an AC compressor spinning at higher RPM's would cool better than one at lower speeds.



~Paul

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'91 300E, 212K miles

**edit .... just noticed that you're saying the reverse is the case. Well that's intriguing.
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  #3  
Old 05-24-2002, 01:40 AM
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Paul - thanks for your post. Although our cars are different body styles, they essentially have the same engine(M103 SOHC). Correct me if yours is the M104.

Makes me wonder if all M103 SOHC cars suffer from this problem? I've read other posts at this site that dealt with inadequate cooling in 124 cars(M103).
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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"
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  #4  
Old 05-24-2002, 09:00 AM
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Many times the "fresh-air" door doesn't shut due to vacuum leaks in the A/C system. That will cause the warmer air to force its way into the car at higher speeds. You can see this door above the blower motor by removing the glove box liner. The door should be completely closed in the OFF position & completely open in the EC position. IF you don't see this change the vacuum elements are leaking.
THIS is only for the W126 chassis!!
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  #5  
Old 05-24-2002, 10:57 AM
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Doc - thanks for the tip. I'll check it out.
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1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"
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  #6  
Old 05-24-2002, 11:21 AM
Mike Murrell's Avatar
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Doc stirred up some recollection on this matter. Check out the following. May be of help to other 126 owners:

http://hsb.baylor.edu/html/easley/autofaqs/recirc.htm
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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"
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  #7  
Old 05-24-2002, 06:38 PM
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Join Date: Apr 2001
Location: Central Oregon
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looks like I will be emptying out my glove box this weekend. :p :p :p

Just more great advice on a superb website!!!

Now if I could only get my broker to give me this good of info !!!
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