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S420
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49 Posts
Discussion Starter #1
The weather turned warmer, tried the A/C today and no cooling. So I checked the trouble codes in the HVAC control and had one...416-coolant circulation pump. I checked the pump (I assume this means the small elec. one) and it's fine. Thinking it could be an old code I deleted it and it hasn't come back.

Here are the values from the A/C control module:
1 - 76
2 - 70
3 - 124
4 - 96
5 - 71
6 - 156
7 - 40
8 - 68
9 - 0
10 - 1.7
11 - 1.7
12 - 4.2
20 - 0
21 - 7
22 - 0
23 - 0
24 - 14.1
40 - 2
41 - 3
42 - 1
43 - 130

I don't have a pressure guage to measure refrigerant pressure, and there is no sight glass, but thought value #7 at 40 bar indicates a high pressure.

All fuses checked OK. The compressor turns but no cooling.

Any clues as to what to look for next?
 

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94 s420 98 s420
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537 Posts
Hey Ray, I converted that bar reading to psi and it was 580.01 not sure if this is way too high or not but you can refer to jims page he goes into deails and all the problems he experienced.


http://pages.prodigy.net/jforgione/AC_Seal.html
 

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SEC 600 V12 2dr COUPE (RHD) One of the chosen few.
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2,233 Posts
Do you have a list of the meanins of the codes.. I posted them on here a few weeks ago..try a search if not get back to me .. i will look them up for you again..
 

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94 s420 98 s420
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537 Posts
here is the link to the codes from jims site. Could a bad sensor be indicating you have pressure, but in reality you dont? Can you check the pressure to confirm the sensor reading?

http://pages.prodigy.net/jforgione/MB_AAC.html
 

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S420
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49 Posts
Discussion Starter #5
I had an A/C service done today. Found the system was down approx 3/4 lbs. I don't know how much of a leak this is since this is the first issue with the system in the 3 years I've owned the car. Now I have a benchmark.

The sensor reading is still a mystery. I remember checking this reading a few years ago when I first learned about the diagnostic system on board, it was the same reading then. It's still the same now. Must be either a bad sensor or control. I dunno...
 
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