1996 Tahoe 4x4, 5.7 v8. Where do you add freon? I read where it was the larger of the two lines off of the evaporator. I thought the evaporator was under the dash? Would this bethe same larger line on the compressor? Hope someone can answer this, as it is still hot down here in Texas. Thanks

 

You should have the system checked out by a professional
You add the freon under the hood at the low side. The high side is the warmer or hot line the low side is the cold or cooler line.
Its added thru the Schrader valve near the front of the engine near the AC compressor.
There are 2 lines the high side and low side both have the Schrader valves,
If you add it to the high side you risk over pressurizing the Freon can and it exploding taking out a hand or two and an eye or two.
You should have the system checked out by a professional
prior to just adding Freon, as just adding it will not fix anything for long, that and just adding the Freon without the proper lubricants can destroy the compressor and its components.
You will also need to verify if you need the R134a or R12 I think 1993 or 94 was the transitional year for the 2 cfc's but I won't swear to it. You also need to know if you need to add the Freon as a gas or a liquid, can upside down or right side up. You should have the system checked out by a professional



EDIT
here are some good sources of info

http://www.familycar.com/classroom/ac1.htm

http://www.aircondition.com/

another good link for doing it yourself, take note of the warnings and cations....
http://www.instructables.com/id/Addi..._Condtioning_/

 

I HIGHLY suggest that you take the truck in if you can't spot the a\c ports under the hood. You can seriosuly harm yourself trying to mess with your a\c

 

Besides hurting yourself, you can also screw up the system if you do it wrong.