Ok, I am sick and exhausted of this climate control at this point. This is one of 3 w204 c300s (2009/2012/2014). It is the 2014, in case that is relevant, and the only one to ever have anything more than a coolant recharge issue. I have the classic issue with the climate control doing the fast blink diagnostic and eventually turning off power to the compressor and going into a slow blink. For the record, I started this journey by checking all the fuses, except the pre-fuse, the charge level of the coolant. Next was the evacuation of the coolant, and replacement of the coolant pressure sensor, next was the replacement of the compressor. I now have a cleaned system, new pressure sensor and a rebuilt compressor that ended up being new from partsgeek. By the way the compressor is of course the one with the magnetic coupling. The only thing weird was the wire connector was a wider 4 prong, so I moved the old cable to the board/selenoid to the new one. It has been recharged with coolant. I have watched the values in the computer and can see the climate control do the fast blink diagnostic, see the amps to the compressor go to 0.98-1.0 while it does startup, then watch it go to 0 and the slow blink when it decides to shut everything down. I am at a complete loss, my next door neighbor is an actual Mercedes Tech and he has nothing to add at this point. The only thing that is off is the cabin sensor with the overhead apparently is broken, but I checked the other 204s and they all have the same bad value in that field. At this point any advice other than have you plugged it in or have you tried turning it on and off would be welcome input. I have haunted this board for years and the advice in here has helped me out tremendously, but never felt I had much to add. This has made me finally make an account and seek out the advice of experts. Please HELP!

 

I'm assuming you have a Mercedes specific obd scan tool you are using.

My Foxwell has an option to show causes for shutoff of the compressor. Tests for various reasons. one thing it shows mention the break-in of the compressor. Im not sure what that is, but did you do some type of break-in with the new compressor?










What about fault codes, does it show any related to the ac or climate control?

You mention you can see the amps at 0.98-1.0. I have only seen mine go up to 0.950 mah. And thats at Max setting. My scanner has an option to function test the compressor. Use the scanner to control the compressor, starting at 0% up to 100%.









And the overhead N70b1 sensor shows very high on mine. Doesnt seem to have any effect on the ac working properly.

 

RELIEF... :
the N70b1 showing numbers off the scale is 100% a scanner incompatibility - It is not a bad sensor.

I used to get that from Autel scanner... until I switched to LAUNCH scanner
Now it's just fine.

 

What type of refrigerant was installed, R134a plus oil? I had warm air coming out last summer and the pressures appeared low so I added a few grams straight R134a. After doing some more research I think I should have also added a little bit of oil also. But thats besides the issue here.

With the climate control ac light blinking it means the car is detecting some type of fault and shutting the compressor down. Have to see what that fault is. I'm sure a scan tool can show what the fault is and reason for the shut down.

The climate control unit (N22/7) itself could be faulty.

You mention replacing the pressure sensor. I'm assuming that is the sensor (B12) located on the condenser? With the engine off and car parked for awhile what does the high pressure read and low pressure read? From my understanding the pressure should be equalized, high and low reading same pressures. I could be wrong but mine seems to be that way. For high side I use my scan tool that shows bar, low side I use a gauge connected to the line, gauge shows psi. So have to convert bar to psi.

 

Wow, that was a comprehensive response, and I appreciate you going through all the screens like that. I use the iCarSoft MB v3.0. As far as I can tell, it does not show or have an option for detecting the reason it is scramming the compressor. I have looked through all of the options, and I can't find anything like that. My next door neighbor is a Mercedes (dealer) mechanic and brought home his in shop computer. We were able to ascertain that the original compressor was "compressor is defective". I ended up buying the denso rebuild from Four Seasons for the 6SBU16C. Specifically the one with the magnetic coupler which after looking in the Mercedes system by VIN was what is supposed to be installed. In the box it had a notice that is was in fact not rebuilt but new due to insufficient cores being available. It was physically near identical with a minor difference in the shield that held the harness. The endpoint on the harness was a few MM wider and had 4 prongs instead of 3. I confirmed with the location I purchased it that is was the right fit for my vehicle. After getting the old one removed, I noticed the difference in the connector, but the rest of the connections were identical so I swapped the mounting plate the connecter is attached to and swapped out the final harness. At this point, I am going to have my friend bring the excel or whatever it is called they use and confirm the reason for the scram on the compressor, if it is 'defective compressor' I guess I am going to be undoing all of this again and swapping the old one back until I can get it returned. Sigh, removing the compressor was not as simple or as easy to get to as all the guides led me to believe, at one point I had a 2+ feet of extensions on a ratchet and a wiggler swivel to get it in and out.