there should be a label under the hood that shows the charge amount. Where do you live? In a w126, r134 may not be good enough to cool you down. I kept my car r12, and it still struggles when its hot and in stop and go traffic, but i am in south texas.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual