AC Repair Part 1

[tiggerkick]

Originally Posted by oldboxster

i reiterate my prior statement;

The pressure reading on the gauges is a function of temperature of the refrigerant and nothing else.

This is a basic behavior of pure component (R134a) 2 phase system vapor/liquid equilbria governed by the physical properties of the refrigerant

The concept is the same as a propane tank used on a gas grill, pressure guages are not fitted to determine the amount of propane since the pressure is constant until all the liquid is gone, for this reason the weight of the tank is used to determine the amount of propane remaining.

I only made these comments in an effort to enhance the understanding of the system by the other readers on the forum.

So I've just filled the car with one can of R134a and the AC feels cooler but I just don't think it is as cold as it can get. The gauge on the canister was almost near "Alert" range. Are you saying that I can pump in another can and ignore the gauges?

[oldboxster]

i presume the "alert" is basically a pressure guage. All automotive AC systems are speced to hold refrigerant by weight, I am pretty sure the boxster calls for 30 ounces. If you dont know know how much was in there to begin with, and how would you, then short of venting the system, drawing a vacuum and then refilling then its pretty hard to know. If you can get a portable temperature measuring tool, often used in food cooking, and stick it in the vent then you will get anywhere from 42-45 DegF on the vent exit with a full charge. Be careful not to introduce air when you are connecting to the system as the air will royally screw things up
good luck

[tiggerkick]

Originally Posted by oldboxster

i presume the "alert" is basically a pressure guage. All automotive AC systems are speced to hold refrigerant by weight, I am pretty sure the boxster calls for 30 ounces. If you dont know know how much was in there to begin with, and how would you, then short of venting the system, drawing a vacuum and then refilling then its pretty hard to know. If you can get a portable temperature measuring tool, often used in food cooking, and stick it in the vent then you will get anywhere from 42-45 DegF on the vent exit with a full charge. Be careful not to introduce air when you are connecting to the system as the air will royally screw things up
good luck

My AC condenser was punctured and let out a stream of the R134a. I've popped in a new condenser and assumed the system is completely empty so I've pumped a can into it so far (18oz). Pelican also mentioned the 30oz the car would take so I guess I'll try and get another 12oz in there. Thanks

[oldboxster]

hello, if you have changed your condensor then you have for sure introduced air into the system as a result of the change over. I recommend you take it to an AC shop so they can check for leaks at the connection points where you installed a new condensor. Once they make sure there are no leaks then they need to draw a high quality vacuum, to remove any air or moisture in the system and only then add 30 ounces of R134a to the system, making sure no air is reintroduced. If you continue to add refrigerant to the system without evacuating it with a vacuum then it will never perform very well due to the presence of the air in the system. Good Luck! As a side note I just replaced a leaky condensor on my boxster along with the receiver dryer, evacuated the system and refilled with 30oz of refrigerant and now I can achieve 41-42 DegF air temp on the exit of the vent with the ambient at about 82 DegF. I think this is pretty good, the car is as cool as I need it to be and the system cycles on and off indicating it is not under a heavy load to achieve this performance.