Kamui

Hello all
I been having AC issues for quite some time now. I’ve researched and talked to many experienced Benz mechanics but have never resolved the issue. I hope someone here may provide with useful information.
Here is the issue, but first I want to point out that this vehicle has been modified through the years and the problem might have started when a face lift was performed for the interior panels (center switches upper panel, AC switches etc.). I have switched to the old AC switches but had the same result.
The AC was hardy getting cold at first. The blower inside the cabin was blowing air but seem very low even when I had selected at the highest setting (max). The compressor was replaced by the dealership (MB) many years back (10 years), and when this did happened, the weather was not really hot. So, the AC was barely kicking in and it was not that noticeable to me then ( I live in California). Then, the AC compressor was replaced yet again by Eurocharged, within or less than a year after having it replaced by MB. When I got the vehicle back, this time it was summer and it was hot, AC intermittently worked on and off got slightly cold and ambient temperature.
Two years ago (to date) I decided to install a Killer Chiller (KC). I then replaced the condenser, dryer, suction hose, performed all the adaptations (valve controlling cabin freon flow and intercooler flow. And most importantly, I bought a new compressor from MB dealership, replaced all O-rings as well. By time tome, the fan blower in the cabin seem to be more responsive and more airflow (volume) was blowing inside. Then, towed the vehicle to one of my trusted mechanic and he serviced the freon. At first, the AC was getting cold (this was in spring time, not hot at all). When it got to summer months, the AC was working intermittently. Took the vehicle to another trusted mechanic who works on Benzs. He tried to service the freon but said the the AC compressor was bad. The compressor was not sucking any freon from the lowside and the pressure was also low. Then, took the vehicle to the dealership (MB), an old pal there spent a lot of time looking at the issue. He thought that by adding the additional lines and the KC might have affected the performance. But, this mods have been performed successfully and since I had this exist issue, I knew it had nothing to do with the additional lines or KC. He then recommended replacing the expansion valve, which it was. This made some difference but not did not fixed the issue. Drove the vehicle close to three years with this AC problem.
So this month, I bought a complete AC system for servicing automobiles. I performed an evaluation of the R134a, and I vacuum the entire AC system on my vehicle. Then, I changed the type of freon and went with one that is similar to the R134a (Envirosafe a replacement for R134a). When I attempted to add the new freon, I noticed that the compressor was not suctioning anything at first, same scenario that one mechanic experienced which he thought the compressor was bad. Then, I persisted in trying to charge the system and turned the AC inside the cabin to the highest setting (fan) while making sure that the AC was actually in the ON setting. After about 10-15 minutes, the air started to get colder and the pressure at lowside was at 38 PSI (when the cabin AC lines were open). When I open the KC lines, the pressure went up to about 48-50 PSI. Meanwhile, the AC blowing inside the cabin was not getting too much colder.
I hope someone here can assist with this as its been a painful experience. Having spent a lot of time and $$$, yet my AC is only performing at 50% of what it should.

Best,

Socal Sam

What is high side pressure? You should be able to feel the cold A/C lines running to the condenser. If so, then compressor side is good and you have a control issue inside. Check blend door actuators. Also check blow motor, resistor, and module. Lastly, when filling system, do not use R134a with sealant. Too many applications will gum up the lines and cause reduced flow. Long shot is the sun sensor located somewhere on the cowl. That provides yet another data point to the computers.

Kamui

@Socal Sam
Thanks for the info above. I have been pretty busy and have not had the time to do any further digging. What I did do this past weekend was, I bought a new Front SAM and configured it. Initially, I had some issues, ignition would not work... I hooked up Start Diagnose and I went through the initial setup. Then, still car would not start and I went back to check the fuses. Turned out that there was many fuses that were missing, that was the issue. Having said that, the new SAM fixed an issues (another issue), which was a persistent acceleration issue that would happen when going about 40-60 MPH. The throttle would cutback momentarily and it was very noticeable (annoying). New SAM made this issue disappear. I ordered a new sun sensor and I should be getting it this weekend.
What I would like to get is the diagram (architecture) of the entire system to start probing. I think that I may have a CAN issue. I have some functions that do not work i.e., door open would not show up on the instrument display, hook open. I am not that familiar with Star, but am planning to start looking into the CAN, I saw that there are many options to change that configuration from the Star Diagnose, but I need to be cautious as I don't want to ruin anything, code incorrectly. What I think I have is coding issues.
If anyone can provide some guidance about going about coding and configuring options (modules for those options) would be great!

Best,

Kamui

Hello all
I wanted to make a quick update on the diagnosis so far.
I did performed a thorough investigation on the high side and side of the AC system. I took various measurements using the manifold gauges. At relative humidity 50% with a temperature of 77 F, my low side was reading 38 PSIG while the high side was at 109 PSIG. According to the chart I have, I should have been gotten between 26-38 PSIG (low) and 120-171 PSIG on the high. Of all the sample I took, it appears that the high side would not achieve anywhere higher than 115 PSIG while within a temperature range between 75-83F temperature.
My investigation process was to look at the hardware components -i.e., AC Compressor, Line integrity, TX Valve, Condenser, and Drier-. All of those components were good as I was able to verified that A. The AC compressor engages which on the low-side reads in the 40 PSIG. I verified that the TZ valve is working nominally by shutting off the AC and letting the vehicle cold down while at the checking on the gauges to normalized to equal pressure (high and low). This vindicated that the TX valve is restricting the passage. Additionally, the second system in the look which can be closed or open independently, perform in the same manner in now achieving the cooling efficiency. For example, at idle when the AC system is fully engaged at maximum cooling, inside the cabin will get to 50 degrees. When driving on the road/freeway, the temperature will read between 42-45 degrees. As soon as it comes to a stop, temperature will start to climb back to 50s.
I even did additional test.
1. I added more refrigerant to the system to see any effects. While performing this the low side did go up to about 50 PSIG while the high got to about 135-150. However, inside the cabin was not being cool and the air was coming in at ambient temperature. The amount of Freon in the system may have totaled to 1.5 pounds, which when I performed an evacuation. I measured about 1.2 pounds.
2. I subtracted Freon and watched the low side pressure ensuring that it go to about 38-40 PSIG (temperature was in the high 70s). The effect from this did caused the cabin to start to cool a bit but no to the point that it was blowing super cold air.
Next. I took out the Star Diagnose System.
I performed a series of test and I was able to resolve other issues not relating to the AC (At least I don't think its relevant). While I was in the ignition (EIS) section, I was able to turn on and off the AC compressor. Initially, I had a lot of different components that were not communicating correctly, so I trobleshoot the issues and resolved them, then clear the codes with respected to the AC. Base on the tool (STAR), I can see that all of the inputs from the sensors were working correctly. See picture of these measures.
What I want to do next is prove the front SAM. I must say that this SAM is brand new, just bought it less than a month ago. In addition, I must also disclose that when I was working with the STAR, I switched to the old C32 AMG cluster and the lower control panel (LCP). What I have been using or what has been in the vehicle is the digital face-lift version which had all the functions of the older LCP. My observation was that with the old LCP I can turn on and of the AC (REST) while the face-lift version did not for some odd reason. The only way to stop the AC compressor for the new LCP was to turn off completely at which point there is not air circulating. Once I did this, I moved into testing with the STAR where I normalized all the motors in the AC system and cleared the codes. However, the results were no different. Another peculiar thing I found with the STAR was that I could not get to the LCP. The system said that it could not recognized it and that the EIS could not communicate with it. This presents a challenge, which is why I connected the old LCP to see if I achieve anything.
After speaking with a foreman at Benz, he indicated that he has no knowledge on coding this module or adapting it. Its rather odd that this is the case as the system should not have rejected the original equipped module (LCP) and I would expect that I could go into the EIS and adapt it but I could not. I get an error (see picture).
So, the plan is for me to investigate the Front SAM and see what kind of voltage I'll be getting (goes into the AC compressor). I also will be installing a new radiator fan as what I got in there right now is acting up but it is on when the AC is on. I am also planning on sending out the instrument cluster (IC) as I need to virginized it so that I can version code it correctly. This was not done as the IC was used and the only thing that could be done then was millage correction. I am thinking that this may add help but am reluctant as the old IC from a C32 AMG did not help with the issue. One thing that cluster did was that it brought some of the functions -i.e., door open, hood open, trunk etc.- Which is something that I do not get from the C55 AMG IC right now.
Apologies for messy write up. I am just so flooded with things that I barely have down time and I been wanted to provide a more comprehensive analysis and write up. I hope that someone here may be able to point me to something or someone that could assist with this old headache.

Best,
LCP COMM error

Pressure Reading (LOW-HIGH)

AC SYSTEM SENSORS

Front SAM DIAG