How can i tell what refrigerant my system uses? Its a 3 ton and ik it uses either r407c or 410a. Cant decide which though. The labels are all either faded or pressure washed off

Is it low on refrigerant? If not what are your pressure readings and how old is it?

What make and year is it ??

These refrigerants have different relationships between their pressure and temperature. You can determine which one you have by taking a pressure reading of the closed system and a temperature reading of the line where you are taking the reading. Then check to see which P/T chart agrees with your readings. You'll need a refrigerant gauge set.

This works as long as your system is "saturated" meaning you have both liquid and vapor refrigerant in the system. Unless your refrigerant has leaked out, you have liquid and vapor.

EPA says you need a license to do this and fines are steep.

Is it air conditioning or is it refrigeration. If it's air conditioning it won't be using 407c.

What is the problem you are having. Check the simple things first such as filters and coils make sure everything is clean. Make sure all your fans are running and all your vents are open if it's air conditioning.

Take a few drops of WD40 and rub it on the data plate - sometimes that will bring a faded one back enough to read it. If it’s a residential unit it’s most likely R22 or if newer 410A. Like already stated you can figure it out as soon as you hook up a set of gauges if qualified to do so or get somebody that is. You can also remove the cover panel over the electrical box (take the power off the unit first at the disconnect) and sometimes the unit model number will be on the wiring diagram - you can have an HVAC supplier look it up and get you the specs if you can’t find it online. Best answer if you’re not an HVAC guy is to have one come out and check it for you.