I have a 1991 300e with new compresser. When the car is at idle or city drive the a/c is not cold or very little cool air is coming out but when i hit the freeway it gets cold. also when i am on the freeway it is not very cold when it is extremly hot outside 100+. any idea what i should do or fix......

your vehicle was equipped with r-12 refrigerant when it left the factory. you mentioned a new compressor, so i would next ask what refrgierant was installed? i'd bet a buck it was r134-a.

fewer and fewer shops offer r-12 anymore. they just don't want to deal with it.

if your system was converted to r134-a, there should be tags under the hood indicating this. if your familiar with r-12/r134-a service adapters, you would know right off the bat what kind of refrigerant you have. some places skip the relabeling part even though they are not supposed to.

i'll be perfectly honest. i have never done a conversion. i have diagnosed and repaired numerous r-12 systems. what i do know "academically" is that a conversion is a multi-step process that requires diligence on the part of the person doing it. i won't go into all of the processes, but a thorough "vacuuming" of the system - removal of old oils, etc and mixing in of oil suited for r134-a is required. there is a lot more to it than just this, but if any part of the conversion is "cut short", you'll end up with a poor performer. a lot of fly-by-night operations skip the vacuuming.

the pressures on r-12 & r134-a differ, so if your system was changed to r134-a, a lesser amt. of refrigerant would have been used....maybe.

someone who can detect what refrigerant you have would install the appropriate gauges and check your pressures - low & high side.

with that information, you'd move to the next step.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

thank you sir for the reply, I wantted to add that yes it has been converted to r134.....

typically i find that you need to maintain 1500 rpm's when temps make their way into the 90's.

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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


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Is the auxilary fan working under any condition ?

Is the belt reasonably tight ? And the pulleys are free of slippery stuff ?

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Saumil S. Patel