unctarheels01

Is there some special way to turn on the A/C? I have a '97 C280 sport, that no matter what temp I have it on on auto, I have no cold air blowing from my car. Is it hard to recharge the A/C yourself? I am just trying to figure this out. I cannot get the car to blow cold unless it feels like it. If I am driving down the highway of a morning, and I have the climate control set on 63, it blows cold, but then it is cooler outside. If I turn it up to 67, it blows cold a little and then blows warm. If I turn the temp all of the way down to the low setting, it still blows warm. I have not heard the compressor kick on, but I am not sure it has not either. When I bought the car it would kick on. I have only had it two months. However, I think it needs recharged. I am not sure though. Just wondering if there is a special trick to turn it on. I have not been successful. Thank you for any and all help. Jeff

GDawgC220

pretty much when the EC light is not on, your on Auto mode, which will get you the A/C. Sometimes the A/C is tricky with the climate control because it's got sensors sensing the temp inside the car and I think it takes the outside into consideration as well. But, if you have it on the lowest setting and it still blows warm air, you may need a recharge or if the compressor is not kicking on, may be a sensor or the compressor itself.

why not bring it into the dealer or a shop to have the A/C tested to see if it needs to be recharged.

mbtech208

The first place I'd look would be the evaporator temperature sensor. Those are common to fail.

Another note: an A/C never just needs a recharge. Refrigerant does not get used up, it leaks out. If you are low on R134, it leaked out of somewhere, and that needs to be fixed first.

GDawgC220

were 97+ using R134 refrigerent?

I thought that earlier w202's were using freon still and converted in the later w202's...

mbtech208

Mercedes has used R134a since 1991.

unctarheels01

Actually, after looking at it yesterday, I found that the compressor is not kicking on. Is there a way to check it for a sensor myself? I like to do a lot of my own minor maintenance before I take things to gt them fixed, so if you know, I would appreciate it. I know that the compressor would kick on during the warmer days during the winter, and would blow cold then, so I am hoping that it is a sensor, or something. Where do I find the evaporator temp sensor? Thanks for all your help.

mbtech208

It's above the driver's footwell. You'll need to remove the lower cover to get at it. It plugs into the heater housing.

pointman

freon?

blackmercedes

You need to have the ACC codes read. There is a keying sequence in the ACC panel, but I can't recall it right now.

The AC compressor in your 1997 car does NOT cycle on and off. Don't think about conventional systems. The car uses a variable pressure compressor that runs all the time. You need to find the pressures and compare them to the operating conditions. If the compressor is inactive or not generating the proper pressure, it can be the evap tem sensor. You can read the sensor in real time on the ACC panel by entering into the diagnostic mode. If the sensor is shot, 99% of the time, the EC light comes on and the sensor readings are REALLY wonky. The other problem could be that your system is low on R134A. Keep in mind that this is a sealed system, and DOES NOT require "topping up." If you are low on coolant and a tech advises putting more in, RUN AWAY AS THEY ARE INCOMPETENT. You'll have to add some dye and find the leak.

In some cars, people thought they were "saving" their compressors by running the system in EC mode wherever they didn't require cooling. This resulted in the demise of their compressor, as it is designed to be run continously. The compressor is lubricated by the R134A (actually, oil in the coolant) and running it is the proper state for long life.

The compressor is not "kicking in?" How did you determine this? Did you check the clutch action? How is your Poly-V-belt? Again, if the compressor is NOT running, this is not normal, NO MATTER the outside temp or cooling requirement. It should be running all the time, and if the EC button has not been engaged, then there is trouble in the system.

Run through the real-time diagnosis (press the rest button for five seconds while the car is running) and check the real time data from the sensors. Then, engage the code storage and find the stored data. Someone else will have to help with that one, I can't for the life of me remember the sequence.

If you are unable to find the problem yourself, or find the process for diagnosis, then take it to a dealer and have the diagnosis performed there. You cold take the "throw parts at it" approach and replace the evap temp sensor and see if that works. If not, well, back to the drawing board...

blackmercedes

Also, you might want to post your problem at:

www.mercedesshop.com

since the quality of the diagnostic and technical info on MBWorld is not nearly as complete as the knowledge of window tinting and body kits. If you need more info on 19" wheels and other stuff, post it here. For hardcore tech info, go to MB-Shop...

Krycheck

I have the same problem too.

I don't drive my C280 as much as I used to. Mostly only on weekends.
I noticed two weeks ago that the a/c slowly stopped blowing cold air. I thought I set something wrong on the controls. I get little cold air but not enough for the 90 degree days we've been having lately.

Looked to see if the compressor was ingaged but I guess now I find out that they run full time on MB's.

Gonna try to take it to my work and see if I can get it checked out for low or no refrigerant.