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Old 02-18-2013, 05:24 AM
rdl rdl is online now
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Location: Ontario, Canada
 
Join Date: Jun 2010
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Mein Auto: 530i 2003
Quote:
Originally Posted by diggyd357 View Post
Not to hijack the thread, but I have a question.... Why must you evacuate the system simply from a low.charge ? I can understand evac if there is no charge or car has been sitting, but topping off refrigerant due to a low charge seems like a harmless solution. Is there something specific to BMW AC systems that I should know about ? Thanks !

#alwayslearning
The ONLY way to ensure a correct charge, i.e. mass of R134a, is to empty the system and and then charge to the specified mass. Pressure readings do not indicate the mass of refrigerant in the system, except to hint at severe under or over charge. People charging by pressure are running a risk, particularly of overcharging which can cause catastrophic damage to the compressor.

Another rationale is that the standard evacuation and recharge cycle includes holding the system at a strong vacuum for some time to check for leaks, i.e. determine if the charge is low due to normal seepage loss of refrigerant over years or an accelerated loss due to a newly developed leak.

While I don't claim to be an expert, I don't see anything the E39's A/C system that is unique compared to other brands. All the components and the system operation strategy are conventional.
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