I've been having a problem with the A/C in my 98 C230 (28,000 miles). The compressor cuts out anywhere from 1 to 5 minutes after the car is started. I first noticed the problem two weeks ago on a trip to central CA for a wedding. The A/C was running fine up to the point where we stopped for lunch. It was blazing hot outside (108 to 110) and the car sat in the sun for about 1 hour. It's black with black leather, which compounded the problem. When we returned to the car the temp gauge on the dash read 120. I'm not sure but I believe that may be where the temp gauge is maxed. After driving the car for several minutes the A/C went out and hasn't functioned normally since. To say the least it wasn't a pleasant drive. The A/C would work off and on the following week but this week it will not run at all, at least for no more than a few minutes. The compressor runs fine (hard and cold) for the brief period following ignition. I'm sure some safety feature is cutting off the compressor, for some reason. I've checked the fuses and looked over the compressor, belt and A/C system and see nothing out of the ordinary.

I've done several searches for related posts and read dozens related to A/C and related topics. One interesting article by Steve Brotherton I came across mentioned something similar with the C230.

"I first ran across these tests while trying to solve a C230 problem whereby its compressor would shut off within one minute of starting. There were some fault codes involved with communication between the fan control module and the pushbutton module. I came across the actual value test while trying to make some sense of the code. I tried the actual values without the engine running. The evaporator temperature showed 155 degrees. When I discovered that the dealer had two of the sensors in stock, I had a good idea that the problem had been found"

This is interesting because (Using the code function threw the climate control LCD) I saw Evaporator Temperature at 145 (function 5, if I'm not mistaken). This while the engine wasn't even running and hadn't been running for hours (temp in my garage was about 75). After starting the engine the compressor kicked in and the evaporator temp still showed 145 to 150. Then out of nowhere it began to drop. It instantly went from 150 to 80 then 40. Moments later it began to go back and forth from 50 to 150, like it was possessed. The compressor then disengaged. The other reading (again using the code function) seemed normal. Refrigerant pressure (code 7) was 4 when the car was shut off and 14.6 while running. Refrigerant temperature (code 8) was 91 with the engine off and 120 on.

I also read in the "Do it yourself" section that this could be caused by a bad belt or by the belt tension being off. What is the likely cause? I'm leaning towards a bad Evaporator temp sensor (given the strange readings). But I'd like to go in to see my mechanic with as much info as possible. Or better yet knowing exactly what the problem is.

Any input would be appreciated. Even if only to tell me that I'm dead wrong and to take the car to somebody who knows what they're doing

Sorry for the length of the post. I figure others with a post W202 might be interested if they come across a similar problem.

I had one of those that I diagnosed right from the actual values displayed on the Pushbutton Controller. I think a description of the event was included in an article I wrote detailing diagnostics available through the PBC (pushbutton controller). It was in the Trade magazine "Import Car" April 2001.

It can be seen at this site:

http://209.115.18.203/editorial/ic/ic40142.htm

The problem was the evaporator temp sensor. It was giving something like 155 deg and I think it was in Celcius.

I just tried the link and for some reason it isn't working. There are descriptions in these archives how to get actual values from the PBC. If you can't get through any of these, write me and I can enclose an attachment with the whole article.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Why they post a link that needs special permission I don't know. The link that does work is very similar:

http://www.babcox.com/editorial/ic/ic40142.htm

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Tradegeek,
Seems like Steve has taken care of you... but just to further assist you, I would check for fault codes in the system.
First of all, see if your poly-V-belt is slipping. Number 52 is for stored codes (on my 95 C280...), hopefully yours is the same... or similar to that. And for me 51 is the number of current slips.
After you do that, have the key in the on position, but not with the car on. Turn the system to LO & Auto. Then press the REST button and the DEFROST (front) for about 5 seconds or until diA appears in the LCD. By pressing the AUTO button, you will come across several codes... record what numbers you get, and post them back. Good luck!
(Hope this was clear.)

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Thanks for the link to the article. That is the same one I found from a post in the archives. I think that is the problem. I ran threw the codes on the climate control screen again with the car running and saw the same action in the evaporator temp. It was at 48 when I started the car and stayed there for about one minute. Then out of nowhere, again, the temp shot up to 145 and I immediately heard the compressor shut off. I know very little about A/C systems, or thermal dynamics, but a change from 48 to 145 in 1 second seems out of the ordinary.

I tried to find the codes that David listed but could not. For 51 (number of belt slips) I get "Lo". For number 52 I get "50 F". And I couldn't bring up the code by pressing REST and front Defrost (with the climate controls set at LO and AUTO on, as you said). I think there may have been changes to the system on post 97 W202s. Does anybody know where I can get a compleat list of code functions for the 98 W202? It would be a big help.

Anything else anybody wants to add would be helpful. Thanks to those that have replied.

Forget what I just said about the diagnostic code not working. I tried again and it worked. The first time I had the engine on. I read over David's post again and noticed he said to have the engine off. I got the numbers but have no idea what to make of them. Here they are.

41.6, 41.7, 41.9, 45.1, 45.2, 45.5, 45.6, 45.7, 45.8.

I put periods where the LCD displayed the symbol for degree (that little circle). From start to end, those are the exact numbers that come up. No more no less. Let me know if anybody knows what they mean.

Thanks

Gosh, I sure didn't read this post very thoroughly this morning. I actually read this and didn't see my name or the reference to my article. I can't imagine it.

You definitely have a bad evap temp sensor. They are cheap and should be cheap to replace. The MB part# is 210 830 05 72 and MB list is $56. The part is fairly easy to replace on the drivers side of the evap case.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Just for info!! The 1996 & later Benzs don't have the belt slippage protection anymore. The only protection is a FUSIBLE link on the compressor clutch, no speed sensor!!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Thanks for the replies. I called my dealer and I'm still under warranty (by less than 60 days, time to buy an extended). I was only able to speak to a service rep who had no idea what I was talking about and didn't seem interested in anything I had to say about the problem. I have an appointment for Monday morning. I'm sure it's the evap temp gauge. Hopefully what info you all helped me with will cut down on the time the car is in the shop. My dealer is just far enough away to make it a major hassle. But at least it's under warranty.

One last thing. Tonight I had the normal problem. A/C cut out soon after ignition. But later when I was driving home I monitored the evap temp while driving. It still bounced around from 40 to 90 very erratically, but never went over 100. The A/C didn't cut out the whole way home (about 20 minutes). That's as long as the compressor has run in weeks. The two times I monitored the evap temp the compressor only cut out when the gauge jumped over 150. That still seems to be the source of the problem.

Thanks again.

In case anybody is interesting (or runs into this post in the archives) the problem was the evap temp sensor. By the time they got to my car it was a quick fix. I was only away from my car for a day and a half. Fortunately, my folks left their Saab in my garage while they were on vacation. I was able to avoid driving that terrible little Toyota my dealer gave me as a loaner last time. I think they loan that thing out just to make sure you'll never buy anything but a Mercedes again. It worked on me Thanks to Steve and David for the help.

Forgive my total ignorance but I do not understand how you
are reading code functions on the A/C system without specialist equipment? Should I be searching archives?

Tigerfox.

Yes,
Search the archives you will find a bunch of info on how to do this. It's great!!
Try keywords like PBU, CODES, N-22 and 202, which the most discussed codes read. Good luck and have fun with it!

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Brilliant David,grateful thanks, it will keep me quiet for a few days

Tigerfox