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  #1  
Old 06-12-2002, 05:05 PM
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190e 2.6 A/C

I've been digging through the archives for information about our wonderful AC systems. I can't seem to figure things out so I'm gonna post let the experts give it a try.

My AC was turning on, and working fine, then would cut out. Had the R-12 re-charged and worked fine for a couple of days. I never noticed it cutting out. Then the hot weather came and the AC would cut out and restart if the car was started. So i went snooping under the hood and found that the Aux fan fuse had an 8A fuse (which was blown) instead of a 16A fuse. Replaced that and the AC was running great, car would stay below 100C even during the hot weather in DC traffic.

Today, the AC just stopped working. I don't hear the compressor turn on when i push the AC button on, and it just blows hot air at me now. No fuses have blown. I have no clue as to what happened. Any advice will be greatly appreciated b/c it's now starting to get a toasty during the days and no AC won't be too fun in traffic.


dan
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  #2  
Old 06-12-2002, 05:13 PM
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Well, I know it's obvious, but make sure the EC button sin't engaged for starters.

Next, turn the wheel to "low" and see if the compressor engages. If not, try the top button on your right hand side of the ACC panel, used for defogging. It engages the compressor for dehumifying. If the compressor engages, then your ACC panel is going south.

If not, could be a compressor problem. Or, you may have a leak, and the system is out of coolant. Since the coolant provides the lubrication for the compressor, it won't turn on when it's low.

You'll probably need to spend a few bucks on diagnosis. Your main components are:

Compressor.
Evaporator. Source of many leaks, and $$ to replace.
Expansion Valve. They wear out.
Receiver/Dryer. Another item (filter) that wears out.
Condensor. These can break too, but not all that common.
ACC Panel. Common failure on W201 and W124 cars.

You'll need to have the high and low side pressures checked and/or the system checked for coolant and leaks.
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  #3  
Old 06-12-2002, 05:21 PM
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Peek in the sight glass, but I don't know if you could see anything worthwile if it isn't running.

And a possible new leak is the fill valve. It may have held just fine but when it was opener to fill it it may not have closed.

A quick check for any pressure in the system would be to quickly and lightly poke a valve and listen for any pressure coming out. Remember you will be releasing valuable freon and you may open a ozone hole over your car (close your sunroof) but it is a test that will tell you something, if you're inclined.
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Old 06-12-2002, 05:45 PM
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blackmercedes

When the AC was working (intermitently) the AC compressor would engage if either the AC button was pushed or the dehumidfy button was pushed. Now it does not work for either. Do you think it might be the ACC panel or the compressor? I'll probably get a Tech to look at it early next week, I just wanted to maybe give him a good description of what i'm experiencing and what it might be.
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Old 06-12-2002, 05:48 PM
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Jim Anderson

Quote:
Originally posted by Jim Anderson
Peek in the sight glass, but I don't know if you could see anything worthwile if it isn't running.

And a possible new leak is the fill valve. It may have held just fine but when it was opener to fill it it may not have closed.

A quick check for any pressure in the system would be to quickly and lightly poke a valve and listen for any pressure coming out. Remember you will be releasing valuable freon and you may open a ozone hole over your car (close your sunroof) but it is a test that will tell you something, if you're inclined.

When the AC was running, I did peek at the little glass on the compressor and saw bubbles swimming on by, not sure if that's normal or means it's low on coolant. I did just re-charge it and i'm hoping it's not a leak. I think i'll leave the testing to the tech's b/c i'm not trying to have anymore repairs then necessary. Especially with this costly AC system. Thanks for you repy.


dan
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  #6  
Old 06-12-2002, 06:31 PM
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bubbles = low coolant.

low coolant = leak.

fix = find leak, fix leak.
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  #7  
Old 06-12-2002, 06:45 PM
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First you must see if the compressor is turning. Next you must see if the PBC (pushbutton controller) is telling the compressor controller whether to turn on. This is very easy, go to the low pressure switch and check that both sides measure the same voltage to ground. They should both be about 0.1 - 0.2v. Now turn the EC position. The voltage should go to battery voltage when the A/C is switched off.

If you have the signal at the low pressure switch (which is easy to get to on the drier I forgot to mention). Then you must go to the Klima or MAS relay (I forget which year we are talking) and unplug it. One should make a jumper with an inline fuse and jump 30 to 87 for the A/C and this will make the compressor come on to verify the refrigerantion system.

If all this goes well you must decide why the Klima or MAS didn't work. If it were my car and it had a Klima I would give it a lobodomy. The technique has been discussed more than once. The up side is no more intermittants. the down side is that one must be smart enough to turn the A/C off when the compressor locks up. Or one has to have the sense to quit driving it once one was so stupid as to not turn off the A/C and now the Alt light and everything else is lit up now that the belt is on the road.
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  #8  
Old 06-12-2002, 11:26 PM
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AC Troubleshooting

Steve, thanks for your reply. The air on my "88 260 does not work either (the compressor doesn't come on). Now I know where to begin troubleshooting.
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  #9  
Old 06-13-2002, 11:48 AM
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Quote:
Originally posted by blackmercedes
bubbles = low coolant.

low coolant = leak.

fix = find leak, fix leak.


well that's not good considering i just re-charged it about 2 weeks ago and that was $100 for just 1/2 pound of r-12. I was getting a little frustrated last night and hit the buttons kinda hard on the ACC panel and actually got the AC to turn on, but then it shortly turned itself off after about 15 minutes. Looks like the panel is the initial culprit, but appears to have a leak as well. I'll definitely be going to a MB tech next week to have this looked at. Thank you everyone for all your help, your knowledge is priceless and extremely helpful.


Dan
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  #10  
Old 06-13-2002, 12:52 PM
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My 02 here. On the 190E, the evaporator (behind the dash) is actually easy to replace (if thats your problem) as there is a sub panel in the engine bay that gives you easy access to the unit. This is not true for the W124 owners, who would need to have the entire dash pulled to have the evaporator serviced.

The evaporator is a common failure point on the AC systems, so its worth investigating.
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  #11  
Old 06-13-2002, 01:50 PM
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Quote:
Originally posted by 2phast
My 02 here. On the 190E, the evaporator (behind the dash) is actually easy to replace (if thats your problem) as there is a sub panel in the engine bay that gives you easy access to the unit. This is not true for the W124 owners, who would need to have the entire dash pulled to have the evaporator serviced.

The evaporator is a common failure point on the AC systems, so its worth investigating.

Thanks, I'll keep that in mind as well when I get it checked out.


dan
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  #12  
Old 07-11-2002, 12:24 PM
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Thumbs up Greased Lighting baby

Well after numerous trips to my mechanic trying to figure out what my AC problem was and many hours searching the web and here for answers...i came across a post where someone just used degreaser on the belt and eureka it worked. Last night i decided to try the mystical remedy and mojo...it worked, AC blows colder than my freezer. So much crap came flying off the belt as it spun and cleaned itself off. Man I wish i had tried this about a month ago.


happy trails,


dan
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