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Old 06-23-2002, 02:30 PM
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Air Conditioning Problem

My 190E A/C runs warmish in slow traffic. In fact, here in Texas it becomes unbeareable in the Summer. The air turns cold once I drive at high speed for several minutes. Is there a problem with my A/C, or it's just the way it works in 190E?
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Old 06-23-2002, 03:10 PM
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I expect that it is slightly low on freon.

Have a great day,
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Old 06-23-2002, 03:32 PM
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Join Date: Jun 2001
Location: Santa Monica, CA
Posts: 2,053
The condensor relies on the aux. fan for cooling at low vehicle speeds. Make sure your condensor is clean and your aux. fan kicks in at the appropriate P/T point (~52* with the red switch on receiver/dryer). If you have access to ref. gauages post the high and low side pressures at 1500rpm. and we might be able to tell more. Mercedes has a reputation in A/C circles for being "condensor challenged", but it shouldn't be "unbearable". R-12 or R-134a
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
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Old 06-23-2002, 09:04 PM
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Join Date: Jun 2001
Location: Omaha, NE
Posts: 962
Mine definitely puts out warmer (but still cool) air when I'm not moving, despite the aux fans being on. The output air is, however, considerably cooler since I got the aux fans to work (had a bad resistor).

You can fairly simply check your low-speed aux fan operation by letting the car idle with AC on on a hot day. The fans should eventually come on at low speed, once the pressure in the system is high enough, unless it's low on charge (or there is a problem in the aux fan circuit).
'93 400E
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Old 06-24-2002, 12:17 AM
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Join Date: Nov 2000
Location: Long Island, New York
Posts: 79
I'm having the same problem with my 1989 300SE. The system hasn't been charged in 5+ years and I'm wondering if a low freon condition will cause this problem as well? (independent of the aux fan)

Thank you.

2004 E320 Wagon
1989 300SE
1998 Range Rover 4.0 SE
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Old 06-24-2002, 09:56 AM
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Thank you for the suggestions everyone. I will have the freon level checked. I don't think the previous owner attended to the A/C for a while since I don't find any records on it.

Pardon my ignorance, but where is the condensor located? And what does the frase (~52* with the red switch on receiver/dryer) mean? I am not sure what switch we are talking about and where that receiver/dryer is.

The car is 1990.

Thank you.
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