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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

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 04-18-2013, 04:53 AM
Fudman's Avatar
Fudman Fudman is offline
Officially Welcomed to the 'Fest
Location: Sudbury, MA
Join Date: Apr 2007
Posts: 6,825
Mein Auto: '02 530i Sport auto
Now here's a thread blast from the past. I resolved my AC problem by simply taking it to my indy for a refrigerant drain and refill. I don't have a vacuum and I can't weight refrigerant so this job is better left to the pros. My system seems to require it every other year, 2010 and 2012 previously but it works fine now (2013). $100 and I am good to go for another two years. Easy day!
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Old 04-18-2013, 08:21 AM
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540iman 540iman is offline
resident, old fart
Location: N.W. Indiana
Join Date: Sep 2008
Posts: 1,873
Mein Auto: 2002 540i sport
Wow, this is an oldie, but I guess I subscribed! The thing that troubles me about your low side pressure is this; it is fine *if* it were with the compressor running and yours hasn't for some time I am guessing. You see, when your compressor is off, the high side pressure and the low side pressure will equalize somewhere in the middle. Let's say that your AC is running properly, your low side of 35# is about right and your hide side using the other posters suggestion of say 100 degrees plus ambient temperature is in the ballpark. So, with unit running you might have 35-175 (low & high). When unit is nopt running for any number of hours, pressures will bleed into one another and your "mixed" pressure may be 70#. The fact that it drops to 35# is proof the compressor is working as it takes low side pressure and compresses it into high side of say 170. You have 35 on low and I bet you have 35# on high side as well if compressor has not run in a while.

See where I am going? Check both low and high with car off since compressor is not running and both should read the same and should be well over 35#. I do not subscribe to "just add more" but I am letting you draw your own conclusion. If you have an equalized 35# with no compressor action, what do you think high and low side would do
*if* compressor could kick in?
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