The A-C in my 2005 Yukon XL is not working front or rear. What should i check first?

the fan isnt blowing? or the air is not cold?

The fan is blowing. The air is not cold.

The freon level is probably low and needs to check/filled at a shop with the correct equipment.

yeah the refrigerant level is probly low, you should check to see if the compressor is engaging.

I'll try that. I had heard talk about certain years of Yukon's having a switch somewhere to change between seasons? I just bought this vehicle in Februrary...

Hey there is bradley stating things that have already been said kudos! I dont know of a switch that has to be changed with seasons sounds silly to me. Very common for a vehicle to develope a leak in the a/c system, being yours has rear air you have alot more lines and a few more componets that could cause problems

that's ok, but at least I didn't tell them that there's still freon in their vehicle which clearly cannot be in the ac system because r-12 was replaced by r-134a

If you would rather call it refrigerant thats fine. Thing is you knew what I was referring to so I wouldn't worry about it too much

here is the definiton: An aerosol propellant, refrigerant, or organic solvent consisting of one or more of a group of chlorofluorocarbons and related compounds. Whats that second word?

it's actually Tetrafluoroethane or r-134a, not Dichlorodifluoromethane or more commonly known as r12 or freon. freon is a chlorofluorocarbon where as the chemical compound used in car air conditioning after about 1990 is not, as it has no chlorine in it.

I dont much care what is has in it. I just work on cars I'm not a chemist who needs to know all that bull. People who work on cars will know what the hell you are talking about weather you call it freon or refridgerant. if it has r12 I call it r12, if it has r134a you call it r134a and if it has r1234yf you call it r1234yf.