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Old 04-12-2006, 04:17 AM
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Join Date: Mar 2006
Posts: 84
Cool air and or A/C problems

My 1989 300E has an a/c problem! When driving the car I turned on the cool air and it was working fine for about 20 min then suddenly very hot air started to come out of the vents. I turned the air off and turned it on again and the hot air was still there. I went home and turned the car off. About 3 hours later I took the car for a drive and the cool air was back. 20 min later hot air again. What could be causing this problem? I changed the push button controls for the heat and the a/c system on the dash and I cleaned out the small sensor on the roof where the sunroof controls are. All out of ideas.

Please Help


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Old 04-12-2006, 08:10 AM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Belt slippage is the most common problem...system monitors the engine speed VS the compressor speed..IF the compressor SEEMS slower the "KLIMA" relay shuts the compressor off until you re-start.
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Old 04-12-2006, 10:00 AM
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Join Date: Mar 2006
Posts: 84
Thanks for the reply but how do I check for belt slipage. I replaced the serp belt 2 months ago and found out that the 13mm bolt that rasies and lowers the tensioner is not working. The bolt just turns in its spot and nothing happens. I had to force the belt on (do not ask how), but this air conditioning problem has been happening for about a year now. When I checked the belt it seems pretty tight.

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Old 04-22-2006, 07:32 AM
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Join Date: Oct 2005
Posts: 128
When hot air starts to come out, is the compressor still running?
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Old 04-22-2006, 08:53 AM
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Join Date: Oct 2005
Posts: 128
I was doing some research on my problem and came across this. There's a tsb for the "Evaporator Temperature Sensor/Switch" that sounds similar to your problem, but mine is on a 1999 C230.


The description they give is:

The A/C system will run for approx. 10 minutes, then the A/C compressor will switch off, and will then run again for 10 minutes after ignition is again switched on.

Maybe it's a similar thing? Good luck,
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Old 04-22-2006, 12:19 PM
bcm bcm is offline
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Join Date: Nov 2005
Posts: 91
I have a 88 2.3 190e,where is that sensor located? because mine does the same thing but only comes on for about 5sec.
Also, curious about how to clean out your compressor & if theres any specail tools to do so?

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