Air Conditioning Problem

[mtavy]

My air conditioning on my 89 190E w /2.6 enging stopped working today.
My wife had the car today and said it was working fine when she went into a store. When she came out no AC. I set the temp all the way down until it locks in like the manual says to do, press the button for cooling, press the AC button, fan speed on high and nothing but hot air. I can hear something engage when I press the AC button. Motor slows a bit. Please help as I have no idea where to start looking!!

[stevebfl]

Which of the vertical buttons on the right are you using. The most assured AC comes from the upper button that looks like defrost. Using te center button requires the mode door to go all the way closed before the AC will turn on. In the upper button position the AC is on in any setting.

If that doesn't matter, check to see if the compressor comes on, if not evaluate the low pressure switch.

[mtavy]

OK. I tried the AC using the top button of the three vertical buttons, the button next to the off button in thr horizontal row of buttons temp wheel all the way in the blue and locked and fan on high. Nothing but hot air. With the buttons at the listed settings and I press the off button and the one to its left ( white rectangle box with two small black boxes on the button) I can hear the engine slow. I assume that is the compressor kicking in. Where is the low pressure switch located and how is it checked? Thanks in advance.

[mtavy]

I went out today to try the A/C and it worked. I started the car, used the same settings as the day before when the A/C wouldn't work, and the A/C worked. The auxilary fans kicked in after a few minutes of running. What should I be looking for as the problem? The air is cold when blowing so it shouldn't need a charge correct? Could it be the low pressure switch as mentioned before and where is it located? Thanks.

[stevebfl]

Read this: http://www.peachparts.com/Wikka/AcDiags and pay attention to the compressor control.

[mtavy]

stevebfl,
I read the post you had listed. I noticied two things that could be related. First, the button with the two small black boxes symbol on the push buttons was moving slowly when disengaged after pressing the off button. It was mentiond that the PUSH BUTTON CONTROL (PBC) could be a source of the problem. Second, the serpentine could cause a problem by not being tight enough causing a comparator test failure in the compressor controller. I just replaced my belt while changing my waterpump. The pointer is broken off the belt tensioner so I tightened the belt to what I thought was tight enough. I will recheck its tension as it may have streched after running awhile in hot temps and let you know how I made out.
Thanks again for your advice.

[mtavy]

My air still works off and on. I took the car to the MB dealer and they could find nothing wrong. I was driving the car the other day and after about twenty minutes into my trip the AC dies when I came to a stop. I read in some posts that if you turn the car off and restart the AC compressor resets itself so that's what I did and it worked. The AC died again that same day but restarted after turning off the car and restarting the engine. I also read the the clutch could be oily. I though since that I cleaned my motor that maybe I got dirt on the clutch so I sprayed the clutch with brake clean and took the car for a ride. After a twenty mile ride the AC was working fine till I slowed to turn in my drive way and the AC died again. I tried restarting a couple of time but the AC didn't restart that time. Maybe I didn't give it enough time to reset. I read in the above article there is a sensor that cuts out the compressor to prevent other damage. I tightened the tensioner by hand and the adjusting screw on the tensioner, then tightened the lock nut when I changed my water pump.
I'm lost as to what the problem might be. Anyone have more advise as to where to look?

[jbaj007]

"The air is cold when blowing"

Does this mean the climate control fan works when the A/C does NOT, as well?

It's not the fan that's not working, is it?

[mtavy]

Correct, the fan continues to run at high speed but the air stops being cold and starts to blow what feels like outside air temp.