Not sure what is going on. Initially it blows cold like normal. Then it gradually warms up as the car heats up. Initially thought it was the Duovalve, didn't look too gunky when I cleaned it. 80f day, a/c set to 65, fan on high. What I have is 120psi both sides with the a/c off. Initially comp kicks in, pressure 48-50/210-225 for about 4 minutes, noise from compressor is less, pressures ~85/160 and the inside air blows lukecold until the next cold start. I ran the fault codes, B1234 and FF are in error. Not sure what FF is, but the radiator fan was running full speed. I think 1234 is the sun sensor, car was in the shade, not sure why that would effect anything. I can download actual values tomorrow, ran out of time today.

I think the actual value readings will help diagnose your problem quickly. Please refer to the 210 chassis a/c diagnostics article here: Service Articles from Continental Imports Put the control unit in diagnostic mode and post up the values of items 1-8. It may be helpful to post them both when first starting the car and the a/c is cool and also after the a/c becomes warm. I am specifically interested in items #3 & 4, which are the temperature of the right & left heater core - this will indicate whether or not your duovalve is stopping hot water flow through the core.

The car started to blow warm air during the warm at 1800 rpm check.

rest start warm idle warm 1800 rpm
1 76.0 75.0 80.0 82.0
2 73.0 73.0 76.0 76.0
3 75.0 57.0 76.0 78.0
4 75.0 53.0 73.0 78.0
5 143.0 139.0 143.0 143.0
6 75.0 93.0 179.0 179.0
7 5.0 10.0 8.0 8.0
8 71.0 111.0 100.0 100.0
9 27.0 32.0 32.0 32.0
10 6.0 6.0 6.0 6.0
11 3.1 3.3 3.4 3.4
12 4.0 4.0 4.0 4.0
20 3.2 3.2 3.2 3.2
21 32.0 46.0 42.0 60.0
22 0.0 0.0 0.0 0.0
23 32.0 32.0 32.0 32.0
24 10.9 13.1 13.1 13.3
40 164.0 164.0 164.0 164.0
41 85.0 85.0 85.0 85.0
42 40.0 40.0 40.0 40.0
43 136.0 136.0 136.0 136.0

Hey, you're fast!

I see a couple of things going on. Based on your pressure readings in the initial post, I think you need a compressor. Specifically, this car has a variable displacement compressor, and I think the mechanism that controls displacement to keep the low side pressure at ~35 is shot. This is reinforced by the data from item 7, whcih shows 10.0 bar of pressure in the system at start, later dropping to 8 bar. Not sure if the compressor control mechanism can be replaced independently of the compressor itself.

The evaporator temperature sensor (item 5 in the diag data) appears to be bad. It shows 140+ degrees consistently. Should start out at ambient and drop to the temp of air coming off the evap - about 35 degrees.

The duovalve looks fine. The heater cores initially drop to ~55 degrees, then rise back up to ambient when the a/c stops cooling.

I'll note that your heater cores drop to 53 and 57 degrees respectively. On this car (w210 chassis) a low refrigerant charge results in only the right (passenger) side of the car being cooled, the driver side gets little or no cooling. So you look to be a bit low on refrigerant. I would not bother to top it up, given the way the compressor is behaving.

Other data from the outside and in-car temp sensors, refrigerant temperature, etc. all look reasonable.

Had 2/3 of a can left I though I would add before it leaked out. Seemed to help initially, blowing much colder but after 5-10 minutes or so the compressor cuts out.
values blowing cold and then after cut out.

1 84 85
2 103 100
3 64 73
4 60 73
5 139 143
6 200 200
7 16 13
8 141 125

Can you look under the hood and determine whether the compressor is still turning when it stops cooling? Does the EC light come on when it stops cooling?

The compressor appears to be operating normally when the car is first started. But then I can't tell whether it shuts off completely or continues running but without doing enough "compressing."

The EC light does not come on. The compressor is not turning when the cooling stops. Sounding more like a control or clutch problem?

After some shipping delays and vacation I finally got the evap temp sensor installed today. Cool Air!! Thanks for the help!!