Does anyone know where to buy cool shot ultra where you don't have to wait a month to get it? I know some of you guys bought it in bulk so wasn't sure if anyone had some for sale?

 

If you don't pull the EVAP I would at least clean it. It's amazing how much harder the fan blows through the vents now, I probably get twice as much air flow which is not surprising considering what my EVAP looked like

 

So I have a question that maybe someone might be able to answer. When I first charge my system I had it on max cool and the highest fan speed, my pressures were on the low side so I added more refrigerant but when I put the dial on regular AC my pressures were way too high. I ended up vacuuming down the system again and recharging it while it was on regular AC and it seems to be doing much better. Everything I've read online says to charge the system on max AC so I'm not sure why I'm getting drastically different readings between the two. Still not sure if I may have messed up the orifice tube when trying to force it into the evap so thinking that may have something to do with it. After I charged the system the second time my pressures are low on max AC but it's still cools very well. I was going by the pressure chart for R134A.
On edit: another variable to the equation is that I put a OBS water pump pulley on a couple weeks ago which doesn't let the fan spin as fast at idle so I'm thinking maybe the reduced air flow across the condenser might be making things screwy. I have noticed at idle my vent temperatures start going up pretty quickly, usually will get 10° warmer ( if I sit long enough) ,until I start going down the road again. I know this is normal because my other truck does the same thing but just not as quickly so I'm thinking that with the reduced air flow at idle and also the fact that I have a fixed orifice tube is why I am getting temp differences at idle. I have heard that variable orifice tubes are supposed to help with this

 

Lets see I'll start by saying that I in no way know any of this to be actually fact. This is just what I come up w/ working through the process of how I understand air conditioning works. So the difference between AC and Max AC is just the exterior vent being open or closed correct? If it's closed the system is forced to recirculate the cabin air and continually bring the temp down. With the vent open warmer outside would be added to the mix and basically allow more heat to be exchanged at the evaporator which would drive the refrigerant pressure down lower. A lower intake pressure at the compressor would also mean a lower discharge pressure. It can only do what it can do provided no other variables change, like rpm. If this is just completely wrong, whomever actually knows what they're talking about please correct me.

 

I see what you are saying but I am experiencing the exact opposite, when adding warm air to the mixture my pressures go up. I'm not sure if that is what is supposed to happen or if I have something wrong.

 

Pressures going up sometimes means freezing up in the evap. I read somewhere while I was going through my system that monitoring temps at the evaporator is actually a more accurate method of charging a system over the "by weight" that is standard. Supposedly all the possible inconsistencies w/ the components and compressor performance make a standard weight not so standard. Again I don't know just throwing stuff against the wall.

 

The most accurate way to fill an AC system is by mass, not pressure. This works best if you start with a completely empty evacuated system obviously.

 

this is how I (my subcontractor actually) does it on all of the ac/r and reefer units I contract for on the bases. He does it all by weight after a full vacuum . On small systems he will pull full. vacuum for two or three hours, on a large walk in reefer he will pull vacuum for a minimum of 12 hours and sometimes up to 24 hours to ensure the system is dry. But gas is always with a scale to makers specs

 

I vacuumed the system down for 3.5 hours The last time I charged the system and that seemed to work really well. The biggest issue with using the small 12 oz cans is that our system takes 3.5 cans and it's nearly impossible to know once you have put the last 6 oz in. Also very difficult to weigh these cans on a scale with the refrigerant hose attached especially if you are feeding liquid into the system with the can upside down. I suppose if I had to do it over again I would find someone with one of the larger tanks of R134A and go by weight. As udsuth said I did see several people online commenting about charging the system until the evaporator tube gets beer can cold which would have put me well under the 42 oz spec that the manufacturer calls for. I kind of charged using several methods at the same time, slowly adding refrigerant watching how much weight I was putting in, the evap tube temperature and the vent temps

 

Yeah, sometimes you just have to wing it.

 

I always kind of wing everything but I am learning about A/C systems a little more this year. My theory is that I can always add a little more. It seems to me that the system needs to run for a little after filling to let things even out so once I have enough refrigerant in there that the system is working, I use it for a while and let it settle down. If it needs more refrigerant, I can add it. I did break down and buy a set of gauges this year but I'll be damned if I can get them to read what 'the books' say they should read. If my dryer/accumulator is cold to freezing and the compressor isn't short cycling, I'm good.