So in my 300D the A/C blows colder on the low setting than the high setting. The P/O had the a/c compressor and such replaced/ charged over a year ago. Should I have the freon level checked? Yes its 134a, wish it was R12 I'm in Houston.

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2001 G500 (45k and counting)
1991 350SDL (211 and counting)
1998 C43 (50k) Silver/Black (sold)
1995 E500 (40k and counting) Pearl Black/Anthracite (sold)
1991 300CE (50k and counting) Silver/Black Cloth (sold)
1983 300D - 79k Classic White/Blue Leather
2002 E55 Obsidian Black/Black
1996 S600 Coupe - 75k Black/Black (traded)
1984 300D -145k (sold)
Silver Blue Metallic/ Blue Leather
1985 300D - 87k (sold)
Manganese Brown/ Palomino Leather
2005 E55, 50k(sold)
Flint Gray/Black

I believe that it takes in fresh air from the outside when it's on "hi". It may be that the slower moving air stays in contact with the evaporator longer and gets cooler.

Seems to be a pretty normal condition.

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My occupational hazard bein'
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1980 300SD
1980 300SD

UM, that would be because the ac system removes only a constant amount of heat from the airflow over the evaporator - a fixed number of BTUs, if you will. That can mean a larger temperature drop for a small volume of air or a small temperature drop for a large volume of air - both represent the removal of the same amount of heat over the same period of time.

See how simple it is?

Got it. Thanks!

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

You've exceeded the system capacity to maintain air temp at high flow, so more flow, less delta T.

It could be that the system was made with just a cap tube for expansion (sized for just one load) and not something like a thermostatic expansion valve (variable capacity to meet variable load).

Reduced cooling could be:
High humidity loading up the evaporator
crap on the condenser / low airflow/ to darn hot at the condenser (houston)



VStech and others can speak w/ more authority than me on matters AC.

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Thanks for the awesome answers guys, however I believe the system is running low on 134a. Will check and post back.

__________________
2001 G500 (45k and counting)
1991 350SDL (211 and counting)
1998 C43 (50k) Silver/Black (sold)
1995 E500 (40k and counting) Pearl Black/Anthracite (sold)
1991 300CE (50k and counting) Silver/Black Cloth (sold)
1983 300D - 79k Classic White/Blue Leather
2002 E55 Obsidian Black/Black
1996 S600 Coupe - 75k Black/Black (traded)
1984 300D -145k (sold)
Silver Blue Metallic/ Blue Leather
1985 300D - 87k (sold)
Manganese Brown/ Palomino Leather
2005 E55, 50k(sold)
Flint Gray/Black