My AC hasn't worked since I got my truck a few years ago. This week I decided to find out why, I took it to my buddies shop to have a look and we ran all the normal tests, charged up the system, checked to see if the compressor was working etc... that done and still no ac we dug deeper, we went to check the orifice tube in the line where the manual said it would be, it wasn't there? it wasn't anywhere?? checked another manual and it said the truck has an expansion block and no orifice tube, the expansion block wasn't there either??? What does my truck suppose to have and where should it be? that is the question. Any help would be appreciated.

 

did you hook A/C gauges up to the truck?..they connect to the lowside and highside. the highside is the liquid line/orifice tube. did you evacuate the system before recharging?

 

Your orifice is in your liquid line on these trucks.

 

It is definitely not obvious that the liquid line from the receiver to the evap has an orifice inside.
Open the hood and stand in front of the passenger side battery. Look down between the headlight and the condenser and you'll see the receiver/dryer where the condenser dumps the liquid into. Follow the other line up and towards the back by the battery where it goes towards the evaporator. THAT line is the one that contains the orifice inside.
The high side service connection is just upstream of the orifice .
When it is operating, that liquid line will be warm upstream and cold downstream of that orifice. There's no getting "to" the orifice like in an old GM A/C.
The aluminum line gets replaced if it needs a new orifice.

Once you locate where it is, you can ALMOST see some marks on the outside where it is crimped to retain the orifice.

You didn't say whether the low and high side pressures where high, low or equal...

 

The system was unable to build any pressure, but the compressor was kicking in and out so we wanted to start with the orifice tube before changing out an expensive compressor. We pulled the lines off to check for the tube, but I will have to recheck the area you are talking about. Thanks Tex!

 

Very common issue is the evaporator core leaking as every little piece of crap that falls in your vents (cowl) end up in the bottom where your evaporator core sits and rots (thus getting a hole). I just replaced it in my '01, along with the liquid line, receiver/drier, and vacuumed and recharged. Just in time too - forecast is for 102* tomorrow in B'more. Uggg!

 

I was going to state the same thing as posted above about the evap coil. Leaves get down there and break down and eat away the coil. I pulled one out of my buddies truck and oak leaves and pine needles galore. Here a pic i took from am chiltons book on where the fixed orfice tube is located.

 

Just to clarify, the entire system DOES hold gas pressure right?

The old compressor COULD be toast and won't pump.
They use PTFE piston rings and when overheated during failure, they will come out through the discharge line of the compressor and lodge in the condenser tubes.. Parallel tube condensers are impossible to clean out and unfortunately must be replaced if the comp did shuck it's piston rings or shed other detritus(aluminum etc).

Pull the lines off the compressor and hand rotate it and see if it pulls a vacuum on your thumb. Do the same for the discharge line and see if it builds pressure. It ought to do a GOOD job of pulling and maintaining a suction on your thumb. If not, it's a worn-out compressor.
If grossly bad, start looking for contaminants elsewhere (everywhere!). Sadly, this is where it starts getting expen$ive with all the new parts.

Don't scrimp! CLean it out well and do it right the first time with a completely cleaned-out pristine system.
(personal opinion: no REBUILT compressors!... go with NEW units only!
I hated it when I had to this difficult job twice...)

Also, I just posted this on another A/C thread, but while you have the system down, before you evacuate and charge it up again, PUT UV FLUORESCENT DYE IN THE SYSTEM... Then go down to Home Despot and buy a compact fluorescent BLACK LIGHT Bulb.
Put it in your mechanic's drop light and look for any leaks at any time in the future.

 

The condensor is new in the last couple years, had a little front end damage and they replaced it with a chinese built unit. We are going to work on it a bit tonight so I will have a look at the rest of the stuff you guys mentioned. if it turns out to be the compressor, I am going to just keep driving with the windows down. Thanks for all the help!

 

Well last week just before I headed off on a 1500km trip I got the orifice tube in and charged the system, blows ice cold. Thanks for all the help guys!