AC not cooling 458

So I did a search, and noted this issue has occurred to others. I would rather save the aggravation of going to a shop to have this looked at if it can be recharged by me, a novice. I found a few items on the net as well as noted here:

https://www.aa1car.com/library/ac_recharging.htm



In 93 you could have R12 or R134a ... R12 is now illegal to use for most cars .. so you would have to have your system retrofitted so it can use R134a ... you can see what kind you have by looking under the hood .. there should be a plaque that tells what kind and how much the system holds .. the R134a systems have a special larger filler port and that is easily recognized by anyone familiar with auto air conditioning .. so just a look will tell them ... R134a is known for slow leaks .. its a small molicule so leaks easily .. the compressor will stop when the pressure gets down too low ..thats to prevent damage .. for now anyone can purchase r134a and many people add it themselves but the law specifies that only certified people can do work on air conditioners .. R12 and R134a are not compatable so you cant mix them .. no matter what the only refridgerrant you can use is R134a.

Regarding the above, I only posted this because it seems to indicate to me the 458 must have R134a and that R134a is a small molecule that is known to leak over time. I know it will list the type under the hood, but the car is in a remote garage. So, is it R134a?

So, I am thinking of buying the gauge, and giving it a go. Anyone else done this?

BTW, our trusted shop says it might even need to be charged to 300 psi depending on temperature. I noted in the link above this:

LOW pressure gauge: When the reading is between 25 and 40 psi with the A/C running, STOP. The system is fully charged and should be cooling normally. DO NOT add any more refrigerant. If the gauge is over 50 psi, you have overcharged the system with too much refrigerant. If your gauge has different color coded zones for R-12, R-134a and/or R-1234yf, make sure you are within the correct range for your type of refrigerant.

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High pressure gauge: When the reading gets up around 200 to 225 psi (R-12), or225 to 250 psi (R-134a), STOP. The system is fully charged and should be cooling normally. DO NOT add any more refrigerant.

NOTE: The high and low pressure readings will vary depending on the system and ambient temperatures (higher temperatures cause higher system pressure readings).

Refer to the vehicle manufacturer specifications for normal system operating pressures, and the total refrigerant capacity of the system. Most newer passenger car A/C systems do not hold much refrigerant (only 14 to 28 oz.), so you don't want to add too much if the system is low. One can of R-134a typically holds 12 oz. of refrigerant.

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So, although this is cringe worthy, if it is this simple, why not try this first. Again, it's about the time and aggravation factor.

 

Thank you, of course it would not be worth screwing it up. That would be even far more aggravation than just an inconvenience