Reply to "Orignal R12 A/C Pressures Readings?"

Is it the term "burst" that you guys are hung-up on? The term burst was never meant to imply dumping freon in at a high rate, or filling any "faster" than "normal". I've used the term burst to infer a differnce in proceedure from filling continuously until a certain pressure or temperature is reached. That's all. As I defined it ... a 1/2 to 1 minute interval and then close the low pressure manifold valve.

Between having the tank valve open only 1/2 turn and only opening the low pressure manifold valve the usual 1/4 turn or so, the gas is flowing into the system at a trickle, very slowly. The amount of gas admitted in that 1/2 to 1 minute interval will not register a decrease in tank weight on a digital scale. Its a slow process filling a system continuously, and filling it in bursts like this only slows the process more. Its a more cautious proceedure than a continuous fill, not the other way around.

The idea is to admit a little gas, then wait for the system to stabilize, admit a little more gas, then wait for the system to stabilize again. The pressures "should" slowly increase, the cold air temp should slowly decrease (I forgot to mention sticking a thermometer in the louver). By filling this way you're slowly nudging the system upward, inch by inch, and standing back and watching what happens. When the temperature stabilizes, the pressures should also stabilize; at that point the system is filled and the cold air will not get colder if more freon were added. If the discharge pressure climbs over 300 psi and things haven't stabilized yet, the system needs repair.

I've serviced the a/c in over a hundred cars belonging to other people (low estimate) over the last 40 years, more in bad condition than good. What I have explained is a more cautious way to fill a system of unknown capacity, in unknown condition, with an unknown amount of freon in it.

-G