AC Recharge with A/C Pro, Blowing Cold but Got a Guage Question - 03 ls v8

[Torx]

ac starting blowing warm last week, with bouts of warm-cool air here and there, but not cold like it should.
fiddled with the ac climate control settings and buttons to make sure there wasnt a glitch to throw the computer off.
started researching the DCCV, but had not yet bought it. Checked the dccv fuse 10a fuse, not blown, still looks great.

went and bought the 20oz AC pro recharge bottle with guage.
cranked up, ac on high, attached to low pres port in the wheel well and followed the directions of shaking and turning and pulling the trigger.

first the guage registered at the #1 spot.
fed it some refridge and it rose up to #2 but then gradually worked itself back down to the #1 spot and it just hovered in that area.
it managed to make it up the #3 spot, but gradually went back down to #1 and just pegged around that area, at this point i heard the ac compressor kick on.
checked the air and it was freezing cold in the car, so apparently it needed a recharge.. now if thats gonna stay i dont know, but at least maybe i know its not the DCCV??

hoping theres not a problem with the guage because the ac system took the whole bottle, and still read #1 until i pulled the hose off and its now reading where its at now. 35psi
air blowing ice cold through both driver and pass vents now.

thanks for any advice or clarification, sure hope i didnt overcharge the system because i gave it the whole 20oz :|

 

[joegr]

A few points.
1. Always set the fan to max, cooling to max, and open the windows when testing/charging the AC.
2. You really should never fill just by looking at the low pressure gauge. You need to monitor the high side pressure too. That's the only way to know if you have it correctly charged. Also, the pressures that you need (both high and low) vary by the outside temperature. There is a factory chart showing pressure by temperature. The LS is variable displacement, and there is just no way to know how much you have put in by looking at the low side pressure only. The whole system only takes 28 oz of refrigerant. If it was working a few days ago and you put in 20 oz, either it is very overfilled, or you have a big leak.
3. You should only use true R-134a. Cans like AC pro have other stuff in there too that is supposed to make it work even better. The truth is that everything that you put in that is no R-134a reduces the capacity and efficiency of the system. This is true of the compressor oil too, but it won't work long without the correct amount of oil.

All that said, maybe it will be okay for you. (Personally, I'd be extremely nervous without knowing what the high side pressure is now.)

4. It's important to look for leaks, because you may have lost most of your compressor oil (common leak point is at the compressor). If you have, the system will destroy itself after a while.

 

[Torx]

Can i use this guage or should i goto harbor freight and buy a guage set to check the high side?

Btw thanks for this info, lol

 

[joegr]

No, the gauge on the can will not work for the high side. Yes, you'll need a dual gauge set.
Here are the correct pressures.
http://deneau.info/ls/s6x~us~en~file=s6xc0006.htm~gen~ref.htm

 

[Andrizzle]

I overfilled mine once, bad times man.