R-12 -- Quantity?

[scottb]

There is a sticker in the engine compartment that says the correct quantity of R-12 in my 84's a/c system is 39 ounces. Bentley's service manual says 42 or 47 ounces (I forget which, and I don't have the book in front of me). What is the correct amount?

Thanks much.

[R22tech]

The correct amount is 39 ounces. However, it wouldn't hurt it to put a few more ounces in. It will leak out anyway, in time, so what will happen is: At first, it will be blowing slightly warmer air into the cabin then as it leaks out, it will blow colder until it gets to the point where the evaporator freezes up and you have no more cooling ability. So, if you are doing it yourself and have the R12, charge it correctly and add when you need to. If someone else is doing it (i.e. you are paying to have it charged), have them put in 43 ounces:it will buy you more time before needing a recharge, thus saving you money.

[scottb]

Since I'm using new barrier hoses, hopefully leakage will be kept to a minimum. Would I be better off simply putting the 39 ounces in to get maximum cooling capacity from the outset? I'd rather have it cool as much as possible (in the Southern California heat) and periodically add some R12 if necessary. Your thoughts?

Thanks.