Safety_Lucas

The AC compressor in my 2013 W204 C350 only works intermittently. When it works, it works well. So I don't think it's a low refrigerant issue. The blower motor also works fine. When the AC button is pressed, I can see the engine RPMs increase slightly, which makes me think the compressor clutch is engaging. But after 60 seconds, if the air doesn't get cool, the compressor disengages and the AC light blinks 3 times. The system won't retry until the engine is restarted. The problem seems to be temperature dependent. The AC seems to work on colder days or in the early morning, but fails when it's warm outside. I'm familiar with working on cars and air conditioners but the dependence on ambient temperature perplexes me. I saw a video on YouTube where a half bearing had come loose from a swashplate in the compressor, preventing it from turning. This gave the same symptoms as my car, in that the clutch engages and the button flashes 3 times after a minute, but there was no temperature dependence. Certainly an obstructed compressor would not magically fix itself on cool days. Has anyone had this problem before or does anyone have any ideas regarding the potential cause of this issue? Thank you in advance!

paulo744

I have 2011 c300 4matic and had a similar issue 2 years ago. When it works it works great, but then on a hot day, or staying in the sun , it wouldn’t work. And once it was working, it didnt stop working in my drive.

i did not have the blinking light issue, at all, so this may be different.

You can try this. on a day the ac doesnt work, and the light is not blinking, turn the engine on and with a small hammer, tap the front of the spinning compressor pulley. It may take a few taps, so tap softly and if you dont hear it click, tap it harder. If it turns on and the inside of the car blows cold, try this next step.

Buy pag-46 oil. Remove the refrigerant. Remove the schrader valve on low side pipe and put im 1.5 to 2 fl oz. Of the oil.

vacuum the system and refill it as close as possible to the required refrigerant. It may be 590g for your car. There is a sticker in the engine bay, near the latch or on underneath the hood. You may need to take the car to a shop who would do this for you.

if tapping the compressor doesnt work, then replace the compressor. Oil will need to be added and it will be good to replace the drier bag in the compressor.

hope this helps and good luck. I had to replace my compressor, but adding oil to the system has saved other ppl from replacing the compressor.

Safety_Lucas

Thanks for the idea. What would tapping the compressor pulley accomplish though? What potential mechanical problem in the compressor could be tripped by hammer taps? Siezed compressor pistons? Perhaps it doesn't work when the ambient temperature is too warm because the PAG oil gets too thin. I suppose it's not too much work to vacuum down and replace the oil and r134a.

paulo744

Not sure exactly why, could be worn out piston seals, sticky reed valves, lack of oil, who knows. Before it gets more expensive, its worth the try

alynch

I would do two things before replacing parts or striking the compressor with a hammer. Connect a set of gauges to measure the high and low side pressure both when the A/C is working and when it is not working. When the A/C light is blinking, connect a code reader and read the fault code. The pressures and the fault code can determine the next steps. If you do not have a set of gauges visit a local A/C shop where they can not only measure the pressures but will be able to determine the amount of refrigerant in the system. You will probably have to only pay for an hour of diagnostic time.