Morabeza

Summary:

in the morning AC was working perfect as normal - started car again, it has ceased to work.
This is a complex situation, so if you're up for a challenge, here's the full version:

Details:
I have a 2005 C230 sport coupe kompressor 140k miles - On Sunday I drove to a car wash with the Air Conditioning working perfectly (It always has, never an issue). I parked the car, cleaned out the interior - I had the dome light on in the rear of the car as I cleaned and the ignition turned just to have some music playing. When I was done I started the car and noticed a short flicker in some of the dash lights and out of the corner of my eye with the rear light in the rear view mirror. There was no sound related to the event. I would have dismissed it as just a lazy turn of the ignition on my part, except I noticed immediately that the Air Conditioning was not blowing cold anymore, and the clock in the dash had reset itself to 12:00. I've been fiddling for a few days now and searching the forums and I cant find anything that explains it. The blower is working just fine.

So far I have checked all of the fuses in both boxes, nothing is broken. I also did the reset by pressing the "front defrost" and "recirculate" buttons simultaneously, it blinks for about 20 seconds and then returns to normal. If I have the "AC off" button on, it is clearly venting the external air into the car. If I have the AC on, then the air seems to be even hotter and more humid than the vented air, I assume because its still running through the system. I visually have inspected the belts, etc everything is running normally - compressor, etc ( of course). I park in my garage and a designated spot at work, neither of those locations have had any drainage or signs of leaking (nor at the car wash when it initially happened).

I can turn the heat on and it works perfectly - all of the vents, direction changes, etc work fine, which to me suggests its not a thermostat issue. I can hear the change kick in when i press the "front defrost", "AC off" and "Recirculate" buttons. When I press the "Auto" button it immediately blows air at high velocity as if its trying to cool the car down, I think that the issue is not related to the controls/buttons.

I have checked all the faults today, and there are 3 on my car - the new one is P0620 - "Generator Control Circuit Malfunction". Ill get to the other 2. So my question with this problem is does it make any sense that the AC is working perfectly one minute and then upon starting the car again it ceases to operate? Would the electrical issue have exposed a low refrigerant level or something that was coming but had'nt shown up yet? Does it make sense to chase the refrigerant levels? Secondly I understand there is no clutch. I read how the compressor could have shut down when there are low freon levels as a protection. Would the same thing have been triggered by the electrical/generator thing? Should it have responded to the reset?

I don't have any gauges to check the pressure myself so my next step is I think i'm going to take it to a shop to have the pressure checked. I hate my dealership, and all of the "german import" mechanics i've tried have been disappointing - but i'm not sure if repair shop that specializes in AC is going to understand the non-clutch compressor or the MB setup.

Side note since I already wrote a novel here, and in case its related, the other 2 codes are P0128 "Coolant Thermostat Coolant Temp Below Thermostat Regulating Temperature" and P0171 "System too Lean (Bank 1) ) faulty MAF (mass air flow) sensor". These codes have appeared since I had the warranty work done last year under the camshaft recall campaign. I had it in twice for them to look at why the codes are coming up and they could never solve the issue. I also had a code immediately afterwards that read for the alternator, but it never repeated, is not showing now, and again i just chalked it up to a lazy crank on my part. So the immediate concern is the air conditioning and what has shut it off. The bigger issue though may be - what could be the source of the electrical / other issues?

Lastly over the last month my car developed a "rough idle" when i stopped at an intersection. At first it did it once every couple days, then every day. It almost felt as if the car was going to stall out, but it never did. While Driving, or in reverse it went as normal, only as I came to a complete stop would it get so rough that I was concerned. If i shifted into neutral or park the rough idle goes away completely, the engine purrs silently as if it were brand new. I had it into the mercedes dealership on a free clinic saturday, and I followed it into the shop to see what they said. They had 10 technicians all gathered around my car trying to decipher - no one said anything looked wrong, and everyone said theyd never heard a car do that. They all seemed genuinely curious but after a half hour of theorizing the manager suggested that was enough free diagnosis and I should come back with a paid appointment if I wanted to go any further. They used some "extendable ears" and thought they had isolated the roughest noise coming from the super charger. They talked too about the motor mounts, but ruled that out because the longer I drove the car in a day, the roughness would fade in its intensity. The reason I mention this is since the AC quit working, the rough idle has discontinued completely. Now the car runs perfectly silent at all times. So something tells me that all of these things are connected to a degree (and are going to be expensive, lol). But again my question is isolated to the AC issue most urgently, and then the electrical fault/rough idle second. THANKS

LILBENZ230

It sounds as though your compressor has seized. All the rough idle things leading up to this point was the compressor seizing up and putting extra load on the engine.

I am theorizing here, but:

If the compressor totally seized up in the moment you restarted your car at the car wash, might that have caused a momentary disturbance in the serpentine belt, thus the flicker of electricity? The A/C compressor is designed not to take out that belt and render the car inop.

That's my theory, anyway.

C230 Sport Coup

Start with the simple stuff. IN regards to the flicker, Did you check the battery cables?
Is there any corrosion? Is there corrosion in the cable itself?

The rest I dunno. If 10 techs couldn't figure it out in 1/2 an hour....
Any issues with belts or pullies?

JFarhanbod

my car has the same exact issue with the A/C. From what I've researched, the alternator pulley goes bad and it basically nukes the compressor. If you replace the pulley and compressor it should work perfectly.

When you look up an A/C compressor for our cars on RMEuropean it says :
"When replacing this A/C Compressor, also inspect the Alternator Pulley. The Alternator Pulley must spin freely in a counter clockwise direction. If not, the Pulley must be replaced. Otherwise the Compressor may fail prematurely."

Hope this helps!

ncmudbug

LILBENZ230 & JFarhanbod are right about the alternator & A/C compressor (ask me how I know - https://mbworld.org/forums/c-class-w...head-unit.html), but it doesn't sound like that happened to you, but is could be. In the first place, I think the tell tale sign that your sprag bearing is going out is a chirping that sounds like a belt slipping or tires rubbing against a rubber floor. That's what happened to me. There were no codes unless they popped after I took it in to the stealer.

Having said that, I wouldn't discount the possibility. If that's what happened, the damage is done and there is no rush (other than to get out of the heat).

If you know a good indy, I would take it there. Make sure they know about the sprag bearing issue. The indy I had used a couple of times (and may not again) hadn't heard of it.

Good luck!

Morabeza

Thanks Guys - the battery connections are clean, excellent idea though, thats a cheap one to resolve. Its funny you said the sprag bearing sounds because that is exactly what happened the last few days - at sounded like a belt or how tires squeak on the painted floor of a showroom. In fact on saturday at the clinic one of the guys said "theres got to be a belt in there slipping for it to make that sound". Mind sharing more of what happened to you - how complex was it for them to fix? what did it run you?

I also should ask - anyone reccomend any Indies in the Raleigh Durham area?

LILBENZ230

This is the first I've heard of an automatic C230 with this issue. The other two guys who have definitely had this issue both had 6MTs and I had pondered if perhaps it was happening only to them. Apparently not.

The moral of the story, if you hear this noise get it into the shop and replace the alternator pulley ASAP or you could end up having to replace the A/C compressor as well.

There IS a reason it is designed this way. Ultimately so it does not strand you, I believe. The manner of how it would fail if not designed this way is a mystery, though.

ncmudbug

Yep, you got caught by that thing, too! Sorry.

It's pretty much all in the thread I linked to, but the short answer is that I took mine to the stealer because I thought that the people who installed my head unit were responsible. I had also had my A/C compressor replaced less than a year before so if it were the problem, the stealer would be on the hook. When my SA told me what it was, I didn't believe him. I mentioned it to an indy I had gone to a couple of times and he had never heard of it (the fact that the guys at the clinic had not recognized it would concern me). I had the stealer do it and it cost $1800 or $1900 (I can't remember exactly - it's in the thread). Good times!

Since you know what it is, I would definitely take it to a good indy if you know one. This might be a good opportunity to find one if you don't know one already.

Good luck and let us know how it went.

LILBENZ230

So you guys are in the same town? Maybe one of you can find an indy. $1800-1900 is way too much, hurts to read about! lol

ncmudbug

My understanding of this is pretty limited, but I understand it has more to do with I4 (inline 4 cylinder) than the 6MT, but I'm not certain. It makes me worry about my wife's car but since hers is a V6 auto - I may not need to worry.

Your advice is well taken. The problem is that it sounds so much like a squeaking belt, it's easy to dismiss (do these cars ever have squeaking belts? with the tensioner, they may not).

I am sure that several people much smarter than I am designed this system and for good reasons - not shredding a belt would be a good one - but I've never seen or heard of anything like this on any other car in the past and I've never heard of a danger of shredding a belt related to either the A/C compressor or alternator... As I said, there is a lot more to it than I know.

ncmudbug

Didn't even notice the last line! I'll PM him.

LILBENZ230

Could it have to do with there being no A/C compressor clutch?

I've not heard about this on a V6 car ever in my tenure here, so I wouldn't worry too much about your wife's car. With its 7G transmission you've enough to worry about in that regard.

ncmudbug

Could be... I have no idea. It sounds like a pretty expensive way to solve a problem that other cars don't seem to have.

I think (and hope) you're right!