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Old 02-18-2013, 07:24 AM
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Originally Posted by rdl View Post
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.

This is correct! If your AC no longer functions, I would recommend taking it to an AC service center to have the proper amount of refrigerant put back into the system. The post-97 e39 requires a narrow range of refrigerant, 750 grams +/- 10 gms. Unless you have the proper tools to perform this service, there is NO WAY you can measure this with a simple pressure gage (ask me how I know). Too much or too little risks damaging the compressor. A slow leak of refrigerant is not uncommon. The leak may take years to manifest itself as a problem (mine takes two years before requiring a recharge).
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