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1989 SEL 560
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I have some questions for an A/C expert before I add the final can of refrigerant. I would like to know if the brass relief valve attached to the drier will prevent me from over charging the system. I have only the one hose that attaches to the can and the low side port. I do not have a Hi/Lo set of gauges to work with. Thanks in advance for replies.
 

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1991 560sec. 1969 280SL
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1,037 Posts
You should if you want a properly functioning ac system have a professional shop evacuate, vacuum and recharge the ac system.
 

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1999 E320, 2003 E320 Wagon, 2005 C230K SS, 2010 Accord LX w Eibach & Koni FSD's
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Did you vac system for 30-45 minutes?

For maximum performance, you will need high/low gauges or shop to do recharge. If you are still on R-12, use sight glass.
 

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1989 560 SEC - V-8 Kompressor - 95 E320 Estate
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I agree with gogi. There are years of information and videos on properly evacuating, leak test and charging an automobile A/C system. Simple system but correct steps are important for good results. With information provided by Tom my only thoughts are to charge until the bubbles in the sight glass disappear and hope you get lucky. BTW adding the correct compressor oil is a must. Some oils only work with R12 and the most common available are for R134 If you have switched over to R134 a perfectly charged system will not perform as well as one with R12 which the original components were designed. Here in the PNW a weak A/C system is acceptable but the closer you get to the equator a system must be dialed in to keep the cabin cool. Best of luck! Mike
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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I would like to know if the brass relief valve attached to the drier will prevent me from over charging the system.
It will not.

The sight glass is useless of you're using R134a. Not sure how it works with Evirosafe. You can get close with the low pressure gauge. You want the low side pressure to be about the vaporization pressure for 36 degrees F, but there is an ambient temperature correction you need to apply, and it depends on what refrigerant you are using.

Here is a chart for R134a:

2613412
 
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