Intermitent A/C Problem ? - PeachParts Mercedes-Benz Forum

Aija · #1 07-10-2002, 10:23 AM

I have a 98 W202.

The other night, I noticed that my a/c was not blowing cold air. The following morning, when I started the car, the A/C blew cold air for about 5 mins. ( I always have it on AUTO 68 degrees), then it was back to 'normal' temperature air again.

So I called my mechanic to set up an appointment for the afternoon. I was praying that my A/C will fix itself, and it did! From the time I started my car yesterday afternoon, the A/C started blowing cold air again. It continues to work fine, so I decided to cancel my appointment with my mechanic.

Does anybody have a comment if I should be concerned? Is there a test that I can do myself to check for some possible problems? Is this a symptom that I should not take for granted? Should I go ahead and have it checked by my mercedes mechanic anyway? I would like to do that, but I am afraid to bring my car to the mechanic, because for sure, he will find something wrong with it(as much as I trust my mechanic).

Thanks for taking the time to read my inquiries. I hope to hear from the A/C technical experts soon.

Best Regards,
AIJA

Aija · #2 07-17-2002, 10:38 AM

My intermitent A/C problem seems to be happening more often that I finally decided to bring my car to the mechanic.

After running a diagnostics on the car (attached the computer), the car did not register any codes. They also checked the freon, pressure, etc. and everything seems to be in order. According to the mechanic, it must be electrical. So they recommended that I bring it in, for them to do a thorough electrical search.

Does my situation sound familiar to any of you? What could possibly be the cause of it? If it is electrical, and yet it does not register any 'problem' code in the computer, what and where are the possible problem areas.

Thanks.

Lonny · #3 07-17-2002, 10:28 PM

Could be a relay

amg280 · #4 07-18-2002, 01:42 AM

It could also be your AC compressor clutch slipping, maybe due to wear or oil on it. Once it slips, the computer shuts the AC off and has to be restarted to work again.

Aija · #5 07-18-2002, 08:38 AM

Thanks for the replies. In both cases you mentioned, would it not register in the computer when my mechanic performed a diagnostics?

amg280 · #6 07-18-2002, 12:16 PM

Thats a good question. Im not really sure. Maybe it wouldnt?

#7 07-18-2002, 10:10 PM

Sounds to be the Evaporator Temp sensor. These are most common. Although, the In-Car Temp sensor could also play these funny games. Both instances generally leave no fault codes and can happen intermittently. Its just a matter of reading their actual values at the right time to pinpoint it. The dealer "should" be able to resolve it quickly. Good Luck!

Bill

Gilly · #8 07-22-2002, 11:04 AM

Aija:
I got your email, I just got back from a vacation in Canada.
I would tend to think along the lines of the evap temp sensor also, your mechanic could watch the actual value of the temp sensor with his computer to verify the reading. Sometimes the evap temp sensor will give a false reading and the control module (which is the actual part with the control buttons on it in the dash) will assume the reading is correct and not set a code. So if the evap temp sensor say "hey, it's -40 in the evaporator section!" the control module will shut off the AC compressor, thinking there's no dire need for any lower temp in the evaporator box, it's plenty cold, too cold in fact. The repair id to replace the evap temp sensor, which is fairly easy, so it only gives the correct reading.
Gilly

Aija · #9 07-22-2002, 11:36 AM

Thank you all for all the suggestions and comments. My intermitent A/C problem was finally resolved on Friday. The culprit is the temp evaporator sensor.

I wish I had waited a few more days before I sent my car to the mechanic so I can narrow down the possible root causes to my mechanic. Maybe I could have save a few hours on labor expenses.

Thanks again.