Does anybody know how I can tell if there is still R12 refrigerant in my 79 Camaro? I'm about to retrofit it to R134A but I don't know how to tell if it still has R12 in it.

PLEASE HELP!!

 

just unbolt one of the connections in the AC system and let it drain

 

Okay, then I can put the R134A kit on and charge it up?

 

yup thats what i did to my aunts caprice and shes got nice ice cold air

just be careful first that gas will be really cold coming out and its pretty toxic so crack the line and walk away

dont completely unbolt the line either just enough that it will leak out you may have to wiggle the lines to separate the oring. ohh and now is a real good time to replace any orings you can get to and the orifice tube

 

You do not want to open a line up. This will allow oil to escape and you will need to try to figure out how much got out and replace it. Drain it slowly at the valve. You really should draw the system down. No air can get into the system. You can draw it down with just about any vacuum pump with the right connectors.
Your system is not designed for the 134 and it WILL bleed down over time. R12 is a much larger molecule then the 134 and the standard R12 lines cannot stop the 134 from bleeding right thru the hose and standard O-rings. The 134 hose have an internal liner to prevent this. You should also replace the orifice tube.
Why are you doing this? If the system still holds R12 why not just top it off?