Most likely it still is R-12. The sticker would or should have been removed. If it was converted the fittings would have been changed but not always the case for sure!

You can have it check with a halogen leak detector. A propane type or electronic one. R-12 can still be had. That has been recycled or from countries that still make it. You may have to shop for the people that deal with. Last I knew it was getting expensive. If you system is tight its the better way to go.

In my opinion some A/C mechanics have to many hoses in their tool box! R-134 was designed to be a drop in refrigerant with minimum change to the system. An oil change out to a different type was all. I think there are brands now that do not even require it. That may be were R-134 (A) comes more into play today.

Either way if it has been change the sticker should hopefully reflect it.

Get with someone that talks only refrigerant and less about a total system change. The more you shop about and become informed. The better you will be!

As far as your system is now. It may be half low on liquid. Depending on the outside/inside temperatures and demand if it works or not. The low side pressure cut out may be stopping it or not enough system quantity & pressure difference.

Refrigerant is like water. It takes it to pull heat out of the fire.

Regards

Phil