Most individual compenents of the A/C (with the exception of the condenser) have been replaced over the last year on my 300D.
Now I get ice cold air like never before when I am driving slowly in city traffic or idle.
However, when I get onto speed on the freeway, the efficiency is much less, it almost feels as if there is 'warm' air coming in through the outer inlets and the center vents are less, also.
What is the problem related to?

__________________
"Schwarzbraun ist die Haselnuss":

1979 300D 234.000 Miles "Brownie"
daily driver,
1979 6.9 Sundays to the Tavern
and car shows "Big Brownie"

could be high pressure switch cutting out compressor, depending on what you have. More information would help, like model, year, refridgerant type, what has been replaced.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

1979 W123 300D, R134, new york piston compressor, dryer, receiver, controls in dashboard. 2 years ago, all vacuum hoses redone. thanks

__________________
"Schwarzbraun ist die Haselnuss":

1979 300D 234.000 Miles "Brownie"
daily driver,
1979 6.9 Sundays to the Tavern
and car shows "Big Brownie"

I'd bet on the compressor shutting down while you are at speed. You may have the "servo" type CCU, lots here has been written about that. I don't know exactly how your system is wired, but I would put a meter in line and measure current through the compressor coil. If it cuts out before it starts getting warmer, you can start tracing why it's getting a signal to turn off. If you have a wiring diagram of your system, that's a great start.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Pete, thanks for your writing. I had the AC Servo replaced with great pains about 2 years ago, also. I was suspecting a vacuum issue, whereas the flaps aren't closing or opening correctly.
Since I have two left hands (with all thumbs on them) I will probably turn it over to my trusted Indy and in the meantime, take slooow surface street to survive a humid summer weekend

__________________
"Schwarzbraun ist die Haselnuss":

1979 300D 234.000 Miles "Brownie"
daily driver,
1979 6.9 Sundays to the Tavern
and car shows "Big Brownie"

You might try blocking your cowl intakes and driving at highway speed and see if anything changes. From your description, the problem could be a ventilation issue, as opposed to a refrigeration issue.

Ventilation would be my guess too. Higher speed forcing nice hot air into the cabin.

Didn't think of that. They are right of course, it could certainly be that, and the price is right on the cost of the test.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

thanks for all of your brilliant inputs

__________________
"Schwarzbraun ist die Haselnuss":

1979 300D 234.000 Miles "Brownie"
daily driver,
1979 6.9 Sundays to the Tavern
and car shows "Big Brownie"

1984 300d Turbo
This May Be A Etr Evac Temp Relay Behind Glve Box $41.00 A Probe Goes In Evac Box Or Temp Control Box Same Place 2 Bolts And
Done My Air Is Cold Now.

Raymond, did I hear you say that you had the same symptoms? Do you have to evacuate the charge to do the job? Thanks

__________________
"Schwarzbraun ist die Haselnuss":

1979 300D 234.000 Miles "Brownie"
daily driver,
1979 6.9 Sundays to the Tavern
and car shows "Big Brownie"