Hi all
I'm new to the board but I have been reading for the past month or so and desided to subscribe, there's a world of valuable information here for those of us who love diesel Mercedes.
My question is the following: My 87 300d turbo has an a/c problem that is baffling me. I bought it about a month ago and have done several little things here and there to start bringing it back. Its now getting hot here in nyc and the a/c does not cool the car near enough to be confortable, I just recharged the system with freze 12, pulled a vacuum for 1.5 hours, purged the lines b4 recharging to get rid of humidity, ect , ect. at idle pressures are 38 low / 170 high @ ambient of 78 degrees. At around 1500 - 1700 rpm they are 32 low and 195 high. Aux fan doesn't come on with the a/c so I have it running direct at the high setting, if you feel the suction line its definitely cold and it sweats even under 80 deg, I get cool air out of all vents but not cold enough to cool down the car and also definitely not enough air volume. The center flap door(the one that reveals the evaporator when open) doesn't open, but even if I open it manually I still dont see a diff in air temp or volume I'm wondering maybe there's an air filter under the dash that is totally clogged but haven't found none, I even get condensate water under the car from the evap, but it just doesn't have enough air volume or is cold enough to cool the car. Hope You guys can help.

check out the the thread "simple ac question". they helped me a lot.

will look for it thanks

Forgot to mention that I checked the little motor that draws air from the interior across that temp sensor that's next to the sunroof button didn't check sensor but there's airflow, has enough suction to hold a piece of napkin against the opening.

The pressures sound a bit off, I expect lower on the low side and higher on the high side. That could be a thing with the refrigerant you are using, I'm not familiar with its p/t curve.

You can't see the evaporator through the center vents, the silver thing is the heater core.

Check to be certain the monovalve isn't leaking and letting hot water into the heater core. If it is, you are (partially) reheating the cooled air. You can run this test by using a pair of vice grips to temporarily clamp off a section of heater hose. Use something to protect the hose from damage - a slit section of rubber hose works well.

The climate system has no filters on this car.

One issue which decreases a/c performance on this car (and all others...) over time is the evaporator becomes coated with dust, dirt, filth, and grunge. It makes a quite effective insulating barrier which prevents heat transfer from the air stream to the evap.

If I had to guess, I'd say your compressor is a bit weak, based on the pressure readings. The system doesn't appear to be undercharged, because the low side reading is plenty high enough - too high, really.

- JimY

thanks for the info I'll check the pump and see if its letting hot water back now that u mention it I do remember having to bypass it with a section of hose on my old 84 300sd in order to get cool air that might be the problem here too