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Old 07-30-2001, 12:54 PM
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Join Date: Jan 2000
Location: Pleasant Grove, AL , USA
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A/C Only blows cold when driving car 93 300 SL

The a/c in my 93 300 SL will only blow out cold air when the car is moving. Whenever I come to a stop the air gets warmer. I also have noticed that the compressor does not sweat hardly at all. Any takers on the problem and should I let a Mercedes dealer look at it or should I try to find a A/C Shop.
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Old 07-30-2001, 03:34 PM
J.HIDALGO's Avatar
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Join Date: Jul 1999
Location: Jax, FL
Posts: 1,785
It sounds like low freon level due to a leak.
Have a good independent MB mechanic look at it. MB dealerships are for warranty work or very last resource.
'86 300E
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Old 07-31-2001, 11:10 AM
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Join Date: Jul 2000
Location: New York, New York
Posts: 179
I've seen this happen when the aux fan doesn't work on hot days. It is the aux fan's job to cool the AC radiator when no air is moving across the coolant. This is the same as the radiator fan for the engine coolant.

That could be your case if this only happens when it is hot. Check the fuses and confirm that the fan comes on. It should only take a few minutes at idle with the AC on for the fan to engage.
'87 300TD 304kmi (RIP)
'95 Toyota Camry Wagon 125kmi
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Old 07-31-2001, 12:10 PM
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Join Date: Aug 1999
Location: Florida / N.H.
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The aux fan for the a/c will not come on if the freon level is low. This is a 2 speed fan , [ low speed for a/c],and it is activated by the high pressure sw. at the reciever/drier. If the freon level is low , this sw. cut in spec. will not be reached due to too low a high side pressure.

I would check both the sight glass for freon level and test the aux. fan circuit by jumping the two wires coming off the high pressure switch. If the fan works with jumper, than suspect freon level low. [ or remote possible bad sw.]

The high speed aux. fan circuit on your model is an aid for engine coolant temp. and is activated by a coolant temp sensor at higher than normal engine temp, regardless of a/c funtion. [ on or off].
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Old 08-15-2001, 02:24 PM
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Join Date: Jan 2000
Location: Pleasant Grove, AL , USA
Posts: 31
I finally broke down and took the car to the dealership. I was informed that the freon was low and that the only way the positively detect a leak was to place dye in the system (for a $175 fee) and allow it the opportunity to work its way through. I was told to bring the car back when I experience the problem again. The system is cooling very good now, however I noticed when looking in the class window on the canister that it boubles whenever the aux fan kicks in. I was curious if this indicated anything or not. Any insight would be appreciated.
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Old 08-15-2001, 03:10 PM
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Location: Florida / N.H.
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That is a good sign of correct charge.
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