sroujiboudy

Hello guys ,

i have a W211 (E350) 2008 model and am facing a problem with my Air conditioning system , sometimes it blows very cold air like freezing ( i like it) and sometimes it gives hot air ( this is the big problem) , sometimes it gives cold air on the passenger side only and the driver side gives a normal air, i already changed the gas and oil in the workshop , checked the compressor pressure it gave 75 ( i think that it needs to be replaced ) i also checked it with the computer it gave me 3 sensor faults :
1- in car temperature sensor : N70b1 -99.0 C.
2-B10/4 -99.0 C .
3-B12/2 temperature valve -99 C.

Any one faced the same problem ? any one have a way to solve the issue ? what should i do first ? should i change the whole cooling system or what ? please help with this matter.

P.S i live in UAE ( Dubai and summer is already here !! and the temperature already hitting 43 C and above , so i really appreciate your fast response

kajtek1

Seem all codes point to the sensor. I think the sensor is in overhead console, so check for loose wire, pull the plug, spray with electronic cleaner and reinsert.
What is the 75 pressure you've got?

sroujiboudy

this one it gave on the LO 75 ( was checked by the workshop they told me that it should be between 40 and 45 )

sroujiboudy

this one it gave on the LO 75 ( was checked by the workshop they told me that it should be between 40 and 45 )

kajtek1

If you want precise advise, you need to give us precise data.
Just becouse you measure the pressure somewhere at some time during the cycle is not telling us anything.
Valid would be high pressure (what you can read on scanner) at max output.

sroujiboudy

to be honest i didn't got ur point , the problem here that i don't have the tools at home and am trying to collect the data from the work shop, and they are not telling me the exact thing ( i know that am not giving exact data , but believe me if i can get them i will not hide any thing)

Ambient temperature 42.4C
B10/6 ( evaporator temperature ) 21.3C
B12/2 Refrigerant pressure 16 bar

Request to A9 ( refrigerant compressor) 70 %
Current consumption of A9 ( Refrigerant compressor 690 mA
Coolant temperature 91 C

This is all the information that i have.

bbirdwell

N70/b1 is located in the overhead control panel; it is an aspirated sensor.
B10/4 is located next to the ignition key slot; it is also an aspirated sensor.
B12/2 is a refrigerant pressure/temperature sensor; I believe it is located at the bottom of the condenser coil and communicates with the left front SAM.

N70/b1 and B10/4 connect directly to module N22, the Automatic Air Conditioning Control Module. N22 communicates via CANBUS to the front SAM which then connects to the AC compressor and to B12/2.

Lo-side pressure of 70 psi indicates the compressor swash plate is at minimum volume displacement. Once the variable-displacement compressor activates and goes to maximum volume displaced, then the pressure would drop down into the 40's. I would hypothesize that since the sensors are providing data that it is -99 degrees C, then N22 "sees" the cold temperature and takes the compressor swept-volume signal down to 2% (effectively not compressing at all).

Keep in mind if it is not the B12/2 sensor you have a possible bad front SAM. STAR diagnosis is the way to go here. If it is a bad front SAM, replace yours with the latest version; there are often multiple updates as design improvements make it to the assembly line.

sroujiboudy

bbirdwell

The shop will need to remove the refrigerant to replace the B12/2 sensor. Before replacing the compressor, first find a shop with an external compressor test tool (such as the Four Seasons 69636 which costs around $477 USD). If they can cycle the compressor swash plate from minimum to maximum to minimum, that will confirm the compressor. Once known good compressor, you're going to have to start digging and that includes using STAR to verify the front SAM again.
Try performing a search on terms such as "variable displacement compressor testing" or "variable displacement compressor diagnosis".

There's a good description at:
www.rbmpartsnews.com/Articles/variable-displacement-a-c-compressors

Please post your solution once you have it. Best to you.

sroujiboudy

Terje Oseberg

I followed the link and read the description and it appears that this is what they're describing.

Pressure Compensated Pump

kajtek1

I am lost in your problem description, so try to make clear what you know. I get your point that you just relay what shops tells you and unfortunately that is not helping us helping you.
My 2008 models no longer has refrigerant temp sensor, when it shows on yours.

Redwood415

Have you removed and cleaned the in car temp sensor properly? If so, why not just replace it if it's giving faulty readings.

sroujiboudy

Sorry for the late response guys , but finally solved the problem and i was out of reach couldn't post before , the problem was with the compressor itself and there was a sensor near the key needed to be replaced , and the problem was solved. thanks for every one who helped and advised