I have a 2001 Mercedes CLK. The other day the AC stopped blowing cold suddenly. I checked the Freon charge and the low side appeared to have way too much pressure. I checked for fault codes, found B1423- switchover valve block (Y11), and checked AC diagnostic data, which seemed fairly normal. I cleared the code and it has not returned. What typically would cause this condition? I have been told it could be a bad compressor or a blockage of some kind. Any help would be appreciated.


Visitor, 2017-08-28

I used to have a 2002 E320 that every year it would trigger that same code. It will happened a couple of times a year so I normally would just reset the code and do the same 6 months latter. The code referes to the valve block Y11 which could either get stuck or has difficulty moving the valves at times which could be due to multiple causes. Considering how old the car is I woudn't worry about it. Just reset the codes when they come up again. If you are concerned replace the Y11 valve block with a used one from a junk yard. Dealer wants a couple hundred dollars for that part which is crazy.

Thanks for the advice. I was not worried about the valve as that fault has not came back. I am worried about the lack of AC probably due to the low side pressure being way too high. I am trying to figure out what {the compressor?} has most likely failed.

When the A/C compressor is not engaged and you try to take a reading via the low pressure port it is normal for the pressure to read very high. Once the compressor kicks in the pressure should drop. At least you don't have a leak in the system. Did the air conditioner start working again after your clear the codes or is still blowing hot air?

MB Fanatic- The AC is still not blowing cold. The reading was observed with the car and compressor running- yes the compressor is still turning on/off. The pressure will drop slightly when revving the engine up but is still way too high for the low pressure side. The aux fan is not coming on with the AC as it does normally which makes me think the pressure sensor has it turned off. I am thinking a seal in the compressor or a valve has allowed the low and high pressure sides to become one. NOTE- this happened very suddenly while driving, AC was working fine then it suddenly wasn't. Any ideas? Thanks in advance.

If the compressor is engaging then yes, you shouldn't have high pressure on the low line. It is very likely that the compressor has failed. You need to connect a a/c manifold gauge set and read the pressure on both high and low side. The A/C system needs proper tools to diagnose. You may want to find a shop that has a scanner that can connect to the 38 pin port and read a/c codes plus experience with a/c systems. Let us know what you find out.

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