92 500SL Air Conditioner Problems - Mercedes-Benz Forum
 
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#1 (permalink) Old 07-01-2009, 09:04 AM
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92 500SL Air Conditioner Problems

I have a 1992 500 SL and for some reason I have nothing but hot air blowing out of the vents. I just purchased the STAR Service - Service Manual Library Model R129 on DVD, but it doesn't have much on diagnosing things. It tells me how to take things apart and put them back together, but not how to diagnose a problem. So, does anyone have any starting points that I should check before I take it in for service? Any information will be appreciated.
Thanks
Phil
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#2 (permalink) Old 07-01-2009, 10:17 AM
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Originally Posted by Phil DeSimone View Post
I have a 1992 500 SL and for some reason I have nothing but hot air blowing out of the vents. I just purchased the STAR Service - Service Manual Library Model R129 on DVD, but it doesn't have much on diagnosing things. It tells me how to take things apart and put them back together, but not how to diagnose a problem. So, does anyone have any starting points that I should check before I take it in for service? Any information will be appreciated.
Thanks
Phil
First thing I would check is to see if the compressor is coming on when the AC is selected. You should be able to observe it engage as well as hear a clicking sound. I suggest you look under the hood while having someone else turn the climate control on with the engine is running of course. Please make sure to take proper safety precautions like keeping hands and other appendages out of the way of moving parts and also apply the parking brake to avoid getting run over. Use of common sense applies here. If the clutch is not engaging the most common cause is the loss of refrigerant. You can check all the fuses related to the Climate control system as well. If the compressor is coming on then it might just be low on refrigerant which would be indicated by the presence of air bubbles when looking into the sight glass located on the receiver/dryer. Depending on what type refrigerant you have you may be able to just top it off (R12 vs R134a). After that if you can not locate the source of the problem it is time to seek the help of a qualified AC tech.

In the event that your system needs to be recharged and you have an R12 type system don’t be pushed into converting it to R134a. R12 is still readily available in the market place and works best in systems designed for it. Simply get the needed repairs and have the system evacuated and charged.

Good luck, I hope I was able to point you in the right direction.

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#3 (permalink) Old 07-01-2009, 11:03 AM
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Check out this link from Bob Terry, it may show you some codes for your HVAC system:
http://www.peachparts.com/shopforum/...ad.php?t=86546.

Matt

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