If the charge faded in less than a season I will use a sealing charge with dye. I filled a friend's truck 2 years ago that wouldn't hold a charge and it is working great in Phoenix

In that case an elbow joint failed and the UV dye clearly marked the leak but also sealed it. I might not use the sealant on a car less than 5-10 years old but when it's 15ish and high enough odds I'll be replacing the compressor anyhow I will use the sealant/dye first. On a younger car I'll use the dye without sealant if the leak is a simple hose fitting I can repair so putting sealant into the system.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)