355 AC pressure help

I am no HVAC expert but recently had to change a couple Freon lines on mine (they had to be cut apart to change the steering rack). The A/C did not work properly since I got the vehicle anyway (which didn't much matter because it's a spider). When we removed the old lines, they were full of leak detection dye and had virtually no pressure. I think the only problem was the Schrader valves leaking (which was masked when gauges were hooked up). After fitting the new lines and valves, it would hold a good vacuum, so we didn't think there were any leaks. Recharged the system and it's stabilized around 45PSI on the low side and 125PSI on the high side. The pressures aren't perfect, but the air is ice cold so we left it alone. The air is so cold, in fact, that when I run the temperature on "cold" override and fan speed of 1 or 2 to the face vents, enough cold air 'leaks' through the defrost vents to create condensation on the OUTSIDE of the windshield. If I run the fan on "high" it would probably keep a frozen margarita frozen - even here in Texas. Sounds like your low side is low, but a dual gauge would really tell you what's going on with the entire system.

 

It could also be indicative of a blocked expansion valve. In that case, yes, the compressor would 'suck' down the low side. What you would see on the other gauge, however, would be a very high pressure on the high side (as all that pressure that the compressor built up tries to go through a blocked valve and can't get back to the low side). Probably worth finding someone that will throw a set of gauges on it and see what it's doing.

 

Nathan, don't go crazy like I did. A trip to Big-O, and $159 later and my car was blowing ice cubes. I took the front covers to expose the a/c ports, they attached their machine, 30 minutes later it was all done. My problem was one of the caps on the low side ports was causing a slow leak of r134.

 

The bubbles indicate gas state refrigerant before the expansion device. There should be only liquid refrigerant to the valve. Carefully add refrigerant until the bubbles subside. At that point you should be right on. Also, make sure your blower is on high and set to recirculate for best charging performance. Of course, this assumes your blower, fans, expansion valve, and compressor are all in correct working condition. If you get a set of gauges that include the high-side pressure you will be able to discover an over-charge condition where you have too much liquid refrigerant backed up in the condenser resulting in high condensing pressures due to lack of change-of-state of refrigerant in the condenser. Good luck.

 

So Big-O can recharge using the older refrigerant? I am kind off Leary of Big-O for my F355. My AC gets luke-warm when it is hot out and get nice and cool when it is warm out. I have a new AC pump that was installed when I bought the car a couple of years back and has never really blown cold on hot days.

 

My a/c never blew real cold air in the 13 years I have owned it. This summer I pinched off the water hose that goes to that "mixer" valve in the trunk. Now my car blows super cold air and I only need the fan on setting 1 or 2 even in 90 degree days. The valve has been leaking and warming my cold air.

 

Where is this valve? Trying to get my AC a little colder for a daily driver in Miami heat!

 

Here is a chart for what high and low side pressures with R134a should be based on ambient temperature.
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