I put 3 full cans in mine to start with and IIRC I had to add a very little bit more from another can when the hotter summer temps came.

 

A few others also said it needs more so I will pickup a can or 2 tomorrow after work.
Thanks
Dave ----

 

Dave,
How many did you put in today? 3 ?
If so just add half a can, then check temp. Add a quarter can then check temp.
It will take time to get down in temp while running.
Make sure the fan is set to it's lowest setting and max ac is set.
I set a fan in front of the condenser to help cool it down faster.

 

I don't recommend filling it and looking at the low side pressure with the fan on it's lowest setting and the A/C on max. All you need to add to that is roll up the windows. Very easy to overcharge in that situation. As the coil gets colder, the low side pressure drops. So you think you need to add more freon. As the coil gets colder and colder recirculatiing the cold air in the cold interior, the pressure on the low side stays low. Once you get out in town on a hot day something is going to happen. Either the compressor is going to lock up or the pop-off valve will blow. Been there, done that. No permanent damage though.

I make sure to roll the windows down, and turn the fan on high, and sometimes I put the A/C on Max, sometimes on regular A/C. I try to get as much hot air as possible into the evap coil when charging the system.

 

The windows were down, fan on high and set to max AC and was 100° in the garage.
Only thing I did not do was fan in front of condenser.
Dave ----

 

I fill all my vehicles with the ac on max with the fan on high and have someone keeping the rpm on 2grand. Never had an overfill issue yet.

 

FWIW: My 1986 factory air truck uses the blue orifice for R-12

 

The one I pulled out looked black, did not know they made a black one?
Also that was a York compressor.
Dave ----

 

My truck's compressor. No markings other than a Ford oval logo.

 

On a 134a retrofit, my system calls for a .067" orifice.

 

What would that be?
Not that I would think of changing it now that I have Freon in the system.
I would have to take it to someone to evac change the valve and put the Freon back in. That would not go well with the wife

Someone on Gary's site posted temp / psi charts and when I can get back on this I can check how my truck compares.
I did pick up 2 more can of Freon and a vacuum check valve.
When climbing a hill or getting on the gas hard the AC air goes to the defrost. I knew the check valve was bad so this new one should fix it.
Time for bed got to get up at 12am and I just walked in the door
Dave ----

 

A quick look around the webs and it appears that a .067" tube is blue.

I guess you have a vacuum reservoir for the HVAC?

 

Granted this is for R-12. My cheat sheet I made back in the 80s when I first got my AC to work properly.

When the truck was brand new I took it to the dealership to complain about the compressor cycling constantly. They said that was normal, an energy saving function. BS. I went home and added some R-12 . It worked as I expected it to, for the next almost thirty years. Gave it a puff of R-12 occasionally, every few years. Always relied on the original sheet.

 

Well that's good it is the blue one, saves me some work.
Yes I do have one, it's a metal can I had to fix as it had rust pin holes causing a vacuum leak.
I do know the factory check valve was bad and now with the windows up I can feel & hear when it switches.
I will have to look at that cheat sheet when on me PC litter hard to see on my phone.
Thanks
Dave ----

 

My overinflated thoughts:

Any AC system is designed to operate with a fixed amount of refrigerant, plus/minus a certain margin. Because the volume changes so much with temperature, the amount is determined by weight. Sounds daunting having to weigh the stuff, but it's not really necessary to be so precise. Those small cans are 12 ounces (weight, not volume as in fluid ounces). I've always guesstimated on getting 11 ounces per can (you can't get every last bit) and then reaching the desired total weight by guessing on a fraction of the final can. For any R134a conversion, a good rule of thumb is 80% of the R12 capacity.

is this method close enough? 38F air from the center vent, you decide for yourself.

Personally, I'm not a fan of filling by pressure. There are just so many variables, especially airflow through the condenser and ambient air temperature. If all components are in perfect condition, I guess it can be done. But let's throw in a common fault, like a little moisture in the system or a slipping compressor clutch. Fill to pressure now and the refrigerant amount could be all over the place, high or low. Besides the original fault, now you've got an unknown quantity of refrigerant to add confusion. You could end up chasing your tail when troubleshooting. Hopefully you will get suspicious by the third compressor.

That's why I like to fill by weight, so you know you've at least got the correct amount if you have to do any troubleshooting. And my weight guesstimation method seems to be reasonably accurate, no scales or special equipment required.