Originally Posted by GMfever
Found another black cap on the silver round cylinder on back left engine compartment (accumulator)?
Then the one (black cap) that is in the line on front left of rad area (line is only about index finger thick).
Find the compressor. You should be able to and if you can't find the compressor.. turn on truck, a/c off, have someone go inside and turn the a/c on and look to see which pully makes the noise of the clutch engaging.
Ok now on the compressor there's going to be two lines coming out of it.
1 one will be fat and one skinny.. (this is compared to each other)
2 skinny line should go to condensor... the condensor is located in the front either behind or infront of the radiator. ANYWAY
3 the fatter line will go backwards towards the accumilator.
make sure your positive you got the suction side, or LOW side (fatter) line.
keep the can upright, that'll put vapor ref. into the system.
if you flip it over it'll put liquid into the system which as we all know a compressor is basically like a 1 cylinder motor so hence putting liquid into it will destroy it.
hope this helps if not try googling low side ac hook up on a 4.2 trailblazer engine.