i have had cars with very slow a/c leaks in the past like lose a half pound in 2 years with that said. my 79 has less than 12 k miles and was stored most of its life and the system worked before it was parked. does it make sense to pull a vacuum on the system to see if it is a very slow leak and possibly just recharge it? also i will not change over to 134a but are any of the r-12 substitutes worthwhile? thanks

 

Not sure I fully understand the situation, but going on the assumption that your system is at this time discharged/non-op, yes drawing down a vacuum is the next step. Not sure what an alternative would be.

You draw it into a vacuum and hold it there for two reasons. One is to check for la leak. If no leak (vacuum doesn't drop at all over 30 mins) you continue to hold it under vacuum (pump running, not isolated as for leak testing) to remove any moisture that got into the system when the refrigerant leaked out and air got in. Moisture is detrimental to ac operation. Under vacuum moisture evaporates away.

Personally, I like the carbon refrigerants (R12 alternatives). They cool better and leak less than R12 or 134A. They are ozone friendly, unlike R12 and non greenhouse gas contributing, unlike 134A. As such, they are not regulated so you don't need a license to buy them. And you can safely and with clear conscience bleed them off to the atmosphere. As such, small leaks are not as much an issue. It's okay to top them up every couple of years.

There only issue is they are flammable. The research done by the manufacturers suggests that a catastrophic event from a flammable substance in the ac system is highly unlikely.

I use them all the time. I know there is some controversy with professional refrigeration guys, but my experience with the stuff has been all good.

Steve g

 

your assumption was on target. and your advice concurred with my thoughts so i feel that is the way to go. thanks for your advice.

 

With the expense of R-12 I'd vacuum it down.... That said, the common leak is the seal on the front of the compressor.

One reason GM went to the AC compressor being on when you put the car in defrost mode was to keep oil to this seal. Sitting is hard on the cars... very hard.

I'd hate to see you charge and lose it... but if it has a leak it will only get worse.

IMHO,

Willcox