I own a 2000 C280 with 208K miles. The AC works for a period of time and then blows warm (Vent Air) After several min the Air blows cold again. This happens on a regular basis. Ive made 3 trips to the dealer for AC issues in 2 months. the first time around they said the system was low on freon and charged it up and added DYE to check for leaks (Works good). Told me to return to look for the leak. When I returned they found no leak and changed the duo valve and a hot water valve. The problem still exists. The next visit the tech then said that the high side of the compressor is icing up due to some blockage.. What could cause this and what is the remedy? I would think that the blockage should be a permanent thing not intermittent. Any suggestions on where to look would be greatly appreciated.

Thanks in advance.

Rob

Almost always caused by Evaporator temp sensor .. MB number 210-830-07-72 list is $37.50

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M.B. DOC, thanks for the reply. IS this part difficult to change and does it require the evacuation of the system?
To further the diag process I spent some time looking for more information and came accross an AC Diagnostinc hidden within the system. It gave indications of various temp and pressure readings throught the system. I will post them. I would appreciate it if someone would decipher it for me. Of all the things worked on with autos for me AC systems represents a very vague area. Here are my readings. 200 C280

In Car Temp = 75 deg
Outside Temp= 86 deg
Heater core Temp = 56 deg
Evap core temp = 59 deg
engine coolant = 204 deg
Refrigerant Pressure = 15.4 bar
Refrigerant Temp = 132

These were taken at idle speed after being on the highway for 1 hr.
The Evap temp at startup (5 min) was 57 degrees
Are these within normal parameters?

Thx

Rob

If it's similar to my 210 chassis, it's not a difficult job. Dash under the steering wheel needs to come off and the sensor is located on the driver's side of the center console area kind of up under the dash. Here's my ecperience with it here - 210 chassis climate control problem

Len

Sokoloff, Thanks for your reply. Im glad you told me where to look. I was about to go hunting under the hood.
Does the information Posted look unusual? After I used the Diag feature on the climate control the system worked continuously for 1.5 hours then went back to blowing warm air for a bit then back to cold.


Thx

Rob.

One more thing I noticed. When looking at the diag screen during the failure (blowing warm air) the outside temp read 116 degrees although it was 86 deg by the dash read out. After I checked it again the temp went back to the correct reading and the system blew cool air for the rest of the evening.
Any suggestions or insights?

thx

rob

M.B.DOC and Len, Thank you for your help here. M.B.Doc I replaced the temp sensor as you suggested and the system seems to be working much better. I only recall the temp getting warm during Idle. After driving off the temp blew cool again. No complaints from the wife is even better.

Thanks

Rob

MB Doc, Sokoloff and Robert,
AC Evap temp sensor reads 149 on my 1998 C280. Went looking for it under the drive side dash, removed the 5 phillips-head screws, and the panel was left hanging with the hood release and the diagnostic module cables still connected to the panel. Was expecting the sensor to be in clear view - However, just could NOT locate AC evap temp sensor? HELP PLEASE - with a picture or a sketch. Thank You