virge

Hi, I just signed up for this forum a little while ago. My 1990 300E was acquired with only minor cosmetic issues and I haven't had cause to complain. I joined just to purchase some wood trim from another member (Hanno).

Today, as I was about to leave on a two hour drive, something broke. The AC had been left on from yesterday. I started the car and before I got out of the driveway, I noticed the AC wasn't cold and the Check Engine light came on. The blower is good but the compressor wasn't running.

I've done a forum and internet search, but I haven't found much to link the check engine light the the AC system. Does anyone have experience with this problem? Any help is appreciated! I'm planning on spending some time on this tomorrow.

HAL STEINER

I have a 94 e320 coupe.
the a/c must be turned off before starting the car or it will not blow cold
something about the way the clutch syncronsizes with the engine
I only know that if I start the car and have forgot to shut it down before I turn the car on it will not start the A?C
the fix for me is turn off the a/c pull over shut off car and restart car and then turn on a/c all is well again
as far as the check engine light this is not related check the codes for this

virge

Thanks for the input Hal. Is that an official start procedure for using AC? Or is it just a quirk that develops in these vehicles? I did not have this problem in the past. Of course, I also do not have much experience with Mercedes.

Either way-- I have tried starting the car first then turning on the AC. No luck, still no cold air and compressor does not run.

I did some further searching and found that since I have a California vehicle, there should be a code light somewhere next to the battery. I will go take a look and see if I can get a reading. The reason I think that the check engine light may be related to the AC is because it came on within minutes of the AC not working. This light hadn't been lit before and I haven't had any other problems with the vehicle.

Will update with codes if I can figure it out.

virge

Check Engine Light: Error code 17

This seems to be related to some kind of control module fault. After doing a bit of searching on the web, I found a post by someone with a similar problem which was resolved by replacing the MAS module. From what I've read (didn't know what MAS was until today) this module controls the compressor operation among other things. A bad MAS would seem to explain my problems...

deanyel

You don't tell us where you're getting the code 17 but code 17 on pin 3 is for the oxygen sensor. You need to build the code reader and pull the codes from pin 14 as well, which for the MAS controller.

virge

I'm getting the code from the LED that's built in to the diagnostic module. From what I understand, think this feature was only found in California cars. Should I be testing each pin separately as well?

deanyel

By 1990 I think they all had the diagnostic connector but may not have had the built in LED. There aren't many live pins on your car but pin 14 is important for the AC, especially whether you're getting code 11-13, and for pin 14 you need to build the flash code reader with parts from Radio Shack. There shouldn't be a relationship between the AC and the CE light, but code reading systems were rather primative in those days. See pages 24 and 28 below. Your car is a 124.030.

http://www.motodok.com/Documentation.../cs1000-mb.pdf