I am considering to buy these items: gauge separately with a couple cans of straight r134a
https://www.walmart.com/ip/Speed-Ste...563#about-item
https://www.walmart.com/ip/A-C-Pro-R...Gauge/36158901
Most of the refill kits that come with the refrigerant and gauge like AC Pro all seem to have stop leak additives. I see cautions about adding the stop leak additive saying it can clog the system and make things worse. And that repair shops will charge you even more if you have used the additives because it spoils their equipment. So I'm really uncertain about using it though many people report good results. What is your suggestion on this ?
I am assuming that I could get some idea whether there is any pressure in the system by just pressing down on the pin in the low side pressure valve, which I did. But no pressure was released. If there were pressure wouldn't you be able to check it this way just to see if its not totally flat ? (OK afterwards i read it's not adviseable to do that, unsafe & illegal to release refrigerant)
If I do use just the r134a alone, don't you still need to put oil back into the system ? If the low pressure switch, transducer whatever shuts down the compressor to protect it when refrigerant is too low, wouldn't you need to add oil back into the system along with the refrigerant ?