Air and moisture will not enter a system which is still under pressure, adding R12 to bring the pressure back to nominal should restore performance, short term. There are two good reasons to evacuate and repair though. The first is that if the system has problems its best to fix them, you are just asking for trouble otherwise - its just a matter of time. The second is that if the system is leaking Freon, an evil CFC, its hurting the environment. If the system had been opened, or if the pressure had bled off and equalized, then there would be air and moisture and untold contaminates in the system. In that case there is lots of work required. In this case the system has pressure, just less than is required to allow it to kick on. The AC on this car presumably did not run for 12 years or so, if there is a leak it has been a slow one. Its also possible that since the car sat for 12 years only 40 feet from a group of 20 or so full time mechanics constantly tinkering, that someone "borrowed" a pound or so of R12 during that time in the late 90's when lots of folks were still driving R12 cars in a world where R12 got scarce and expensive. I know that's what happened to the original radio - someone decided it was better off in their car than in mine. This is further bolstered by the fact that the service caps for the ports were sitting in the engine area when I found the car, not installed on the ports. Wishful thinking maybe but hope springs eternal. Even if the system has not leaked, it is possible that as soon as the pressure goes up in it for the first time in years that it will then start to leak. No way to know. Ultimately I want a perfectly operating system, and I'm hoping the system holds the R12 nicely until I have the time and resources to rebuild the system. In the meantime its nearing 100 degrees here every day now and if I'm going to get this thing on the road, then I'm looking to put a can or R12 in it to see what it does. Tom 10902 -----Original Message----- From: John Macias Subject: [DML] Re: R-12 Certification and purchase I thought that "topping off" a system was a bad thing, and it needed to be completed evacuated? I am incorrect? To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/