THanks for clearing that up Mike.
Ok, I will do the test tomorrow. I will do it while the engine temp is normal, about 87 C. I think I will try using my climate control to get the temp of the AC first. If for some reason I can't get it, then I will get a thermometer.
Nice little feature to have all of the data read out of the climate control when I need it!! Thanks everyone for the help.

(Still anyone know where the freon glass is in C280?)

Can't help you on the sight glass David.

Doesn't your readout only tell you the cabin temp? You really need a thermometer to stick in the A/C vent to get a proper reading. Remember, once the chilled air leaves the ductwork, it is warmed by the cabin air, which in turn is warmed by solar energy via the window glass.

Now if we could only turn that solar energy into motor fuel, we wouldn't need gas, 300 days out of the year here in SoCal :eek:.

Sight Glass
 

David,

Have you looked behind the driver's side headlight assembly? That's where mine is located. It looks like a round tubular assembly with a small (1/2" dia) glass on top.

BTW, MB specs says you should hold the engine at 2000rpm for that test! Also my engine temp was 85C and I did NOT do it at 2000prm but at idle.

Here are my results. Though I used the Climate Control to get the temperature; I didn't put a thermometer in the center vent. It might be a little colder assuming the sensor is down in there.
With climate control on AUTO and LOW... when driving (roughly 30 mph), on low fan speed, the temp is between 35 and 42 F. When it's the fan is on high speed while driving, it is about 41-46 F.

Alright, now when I'm stopped, with the fan on high speed, the temp is between 48 and 54. While stopped with the fan speed on low, the temp is between 41 and 48 F.

Seems fairly normal to me I guess. But this is using the onboard temp sensor.

Thanks everyone.

Simply spring the bucks for a service. R134 pressures are higher that R12 and hence seepage from the system is inevitable. To boot, the C280 only takes a bit over a pound of refrigerant. Any leakage at all will degrade performance. Fortunately, the compressor has plenty of protection to keep you from running it with too little coolant. It simply wont run when pressures drop too low.

My 560sl is showing a max cooling temp of around 50degrees. What should I check first..Do I have the window to check for bubbles? The car cools a little better when the rpm's are higher.
Any suggestions?
What does it cost to switch from r12 to r32?
Thanks,
rob

I believe the conversion is not much at all. I think it is like $50 or something like that.

I am sure much of the advice in this post should help you start looking to improve your AC.

AC temperature
 

Note that cars that have been converted from R12 to R134 generally do not get quite as cold. The air from the dash will be about 12% warmer. This is the cost of being "environmentally friendly" I guess.

Ok,
I just checked out the glass covering on the compressor, or what I think is the compressor. It was under the hood, driver's side, behind the headlight, down at the bottom mounted to the frame. It was really dirty but I cleaned it so I could see through it. I then turned the car on and looked through the glass. About 3 seconds later, I saw something like smoke, or what it looked like whizzing up towards the glass. I then checked the temperature via the climate control (N22 read-out) and it read about 45.5 degrees F. So system seems ok.
Question is that it didn't look like there was water in through the hole, should there be? Or maybe I just coudlnt' see it, and there were no bubble; that must be a good thing.

Smoke in sight glass
 

I think what you are seeing is normal. The freon, when under pressure is a gas.