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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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Old 11-27-2012, 07:56 PM
ourcookie ourcookie is offline
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Location: Los Angeles
Join Date: Nov 2012
Posts: 8
Mein Auto: 1997 540i
a/c climate control is abnormal

Hi, I suspected my ac system in my 1997 540i doesn't work properly. When I turn on a/c, it doesn't matter what temp I set, ranging from 60F to 90F, there is no different in the air temperature coming out from the vent - it is always cold. the only way I can lessen the air temperature is by turning the round wheel on the air vent from say, 3 blue dots to 1 red dot, then I can feel the cold air lessen. Does this sound normal to you guys? Normally, shouldn't changing the temperature's degree would alter the air temperature?

Any comments would be helpful. Thanks
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Old 11-27-2012, 11:22 PM
edjack edjack is offline
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Location: San Jose, CA
Join Date: May 2007
Posts: 13,455
Mein Auto: '97 540i 6 speed
Mine works the same way: the A/C outlet temp is constant; the blower speed changes with cabin temp. However, the heater does change outlet temp according to cabin temp.

I suspect that later years had a blending function for the A/C. Perhaps someone can chime in here.

Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.
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Old 11-28-2012, 07:23 AM
mbell666 mbell666 is offline
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Location: Austin, TX
Join Date: Jul 2012
Posts: 220
Mein Auto: e39 2002 540i6
What is the air temp out of the other vents like?

The central vent is "special" and can output heated/cooled air or external air depending on the position of the dial. I can't quite get my head to remember how positions relate to external/conditioned air thou.

Does the heating function work with AC off?

AC system normally chill the air then use the heating matrix to warm it back up, if the heating system isn't working the system will always blow cold.

Have you got a temperature gauge you can use to measure the output air temp? It's hard to monitor changes just feeling with your hand.
An e39 is like a beautiful wife, needs constant attention, lots of money, lets you down at the worse times but you’d never be without it.
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Old 11-28-2012, 07:29 AM
cn90 cn90 is offline
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Location: Omaha NE
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Mein Auto: 1998 528i 5-sp 140K+
Normal design for the center vent.
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Old 11-28-2012, 08:05 AM
isaac540 isaac540 is offline
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Location: Nashville, TN
Join Date: Aug 2012
Posts: 36
Mein Auto: 1997 540i
I believe this is normal for the earlier model e39s.
I know my '97 540 will blow hot air if I turn the dial to the red even if the A/C is on (I leave the A/C compressor on all the time because the bump in idle speeds keeps me from getting this stupid flickering oil pressure light, but that's an entirely different problem).

Anyway, I don't think you actually have a problem here. If you want hotter air, adjust the dial between the vents to the red, not the actual climate control temperature. I usually keep the climate control at 70° F and that keeps the cabin at just how I want it.
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