My ac is not working, I want yo put some dye in it. R12 is not so easy to come by, can I put some of that freeze12/dye or something cheaper and easier to come by to help find the leak?????

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1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6