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So then, what options do I have?

My A/C functions, but it's not very cold.
Typically when people top off with the can, it works great for a season and then next year same problem.

If you've lost charge you have a leak.

Only way to determine current charge is with a recovery machine or recovery tank / scale. You will find a low charge. Pressure test and check for leaks. Replace Schrader valves. Vacuum below 500 microns and then re charge to the level indicated on the radiator support tag.
 

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its still not going to be a truly accurate charge


You can weigh a 12 oz. Can the same .. all you need is a scale. 😉

1997Thunderbird - I build large scale commercial refrigeration systems, by the way .. same difference.

All you need is: a vacuum pump, dual needle gauge manifold and hose set, scale, and micron gauge. Most people don't have or want to invest in this equipment .. it's not cheap.

Matt's method is the most conventional / economical way to get a good charge but you still need the proper tools - depending on your auto stores, some or all are available to rent.

Edit: if you want to find the leak, you may need a bottle of Nitrogen and regulator setup as well.
 

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I mean if you "top it off", there's no way of knowing how much refrigerant is left in the system to know how much weight to put in from the 12oz can(s). Doing it the right the system needs to be fully evacuated, legally and ethically requiring a visit to a shop to pull it one way or another, from there you can do it yourself using all that stuff to refill after finding/repairing the leak source.
Correct. See post #7. Topping off a leaking system won't make a difference in charge amount when its going to come back out anyways - it only verifies that the system is leaking and then the moral / legal obligation is to have it repaired. This only applies if you have the Section 608 ( Types 1-3 ) or Section 609 ( mobile ) certifications. 😉
 

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You should expect around 20-30 degree Delta T ( the difference between outside ambient temp and air out of the vents. That is with a fan blowing on the front end of the car or while driving.

The can will charge liquid if you hold it upside down and gas in the upright position .. for example if you were charging and the pressure spikes to 45+ on the low side with a liquid charge you can turn the can sideways to go between gas and liquid .. that is until your low side pressure equals the pressure left in the can = 30 psi not moving is not necessarily an empty can but it won't suck or push any more refrigerant into the system.

My Auto HVAC instructor would tell us "there is no such thing as cold air .. just air with less heat in it."
 
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