Orifice Tube?

[dcurtis]

Where does the orifice tube go? My car is a 91 GT if that matters. Pics would help if you have them.

 

[dcurtis]

I pulled my whole ac system off and had it all cleaned out because it is apparently clogged or something somewhere, any way I pulled the ac line that is at the front passenger side going into the radiator looking thing (can't remember what it's called) and there was an orifice tube in it where you attach the line to the radiator looking thing, the orifice tube was in the top line, I was told by someone that it should be in the lower line that runs to the ? on the firewall, that line has a 4 or 5 inch long piece of steel tubing in the middle section of it and that is where I was told it should be, is this right, does the lower tube have a fixxed orifice tube in it already? Sorry if this sounds confusing but I don't know much about ac systems.

After I cleaned the entire system I recharged it with new oil and 2, 12 ounce cans of refrigerant, I had the ac on max and the car at an idle when charging it, any way the ac took the refrigerant just fine and the ac was blowing super cold again, tha was until I gave it a little gas and it blew off at the release valve on top of the compressor, which is why I cleaned the system in the first place, but it still does the same thing, it will take a charge but as soon as I give it any gas it will blow the refrigerant right back out, I only have the rev it to about 1500 rpms for it to blow off, what could cause this? Someone please help because I would realy like to use my ac while driving and not just at an idle

 

[Saleen0679]

The orifice tube should be in the lower line (liquid line) that goes to the evaporator. AFAIK the orifice tube in the Fox cannot be changed out without using a cut and splice kit. Otherwise the whole liquid line must be replaced. Hopefully someone will verify.

 

[dcurtis]

That is what I have been hearing also, is it possible that the orifice tube I found was creating the excess pressure causing the blowoff? The liquid line is a new line that the last owner installed, and a few people have said there is already a orifice tube in the line and that I didn't need the orifice tube that I found, not to mention I found it in the wrong line.

 

[Saleen0679]

I only know the basics of the A/C system, but I expect that putting an orifice tube in the upper line would put an obstruction in the high pressure line and block the entrance to the condenser causing a back-pressure problem at the compressor causing the blowoff.

Where are the A/C gurus when you need them? I know there are a few on this board.

 

[jrichker]

From the Ford manual...

Fixed Orifice Tube

The fixed orifice tube located in the liquid line cannot be serviced in detail as a component of the line. If replacement is necessary, the line and tube must be replaced as an assembly, or an orifice tube replacement service kit may be used as an optional service procedure. The procedures for each type of service follow:


Liquid Line and Orifice Tube Assembly Replacement

1. Discharge refrigerant from A/C system following recommended service procedures. Observe all safety precautions.

2. Disconnect refrigerant line at condenser outlet connection using procedure and one of spring lock coupling tools shown in the Spring Lock Coupling illustration.

3. Disconnect refrigerant line at tube-O end using a wrench on each side of tube-O fittings. Remove line from vehicle.

4. Route new refrigerant line (and integral fixed orifice tube) with protective caps installed.

5. Remove protective caps and connect new refrigerant line into system using new O-rings lubricated with clean refrigerant oil. Connect spring lock coupling as shown in the Spring Lock Coupling illustration.

6. Leak test, evacuate and charge refrigerant system following recommended service procedures. Observe all safety precautions.

There is a reapir kit to replace the section of tubing that has the fixed orfice tube.

Fixed Orifice Tube Replacement Kit

1. Discharge the A/C refrigerant system. Refer to System Discharging in «Section 12-00». Observe all safety precautions.

2. Remove the liquid line from the vehicle.

3. Locate the orifice tube by the three indented notches or circular depression in the metal portion of the liquid line.


Orifice Tube



4. Note the angular position of the ends of the liquid line so that it can be reassembled in correct position.

5. Cut a 63.5mm (2-1/2 inch) section from tube at orifice tube location. Do not cut closer than 25.4mm (1 inch) from the start of a bend in tube.


Orifice Tube Section Removed From Liquid Line



6. Remove orifice tube from housing with pliers. The orifice tube removal tool cannot be used.

7. Flush the two pieces of liquid line to remove any contaminants.

8. Lubricate O-rings with clean refrigerant oil and assemble orifice tube kit (with orifice tube installed) to liquid line. Ensure flow direction arrow is pointing toward evaporator end of liquid line, and taper of each compressor ring is toward compression nut.


Orifice Tube Kit--Disassembled



NOTE:
The inlet tube will be positioned against the orifice tube tabs when correctly assembled.

9. While holding hex of tube in a vise, tighten each compression nut to 88-94 N-m (65-69 lb-ft) with a crowfoot wrench.


Tube Kit Installed



10. Assemble liquid line to vehicle using new O-rings lubricated with clean refrigerant oil. Use only specified O-rings at spring lock coupling.

11. Leak test, evacuate and charge system following approved procedures.

12. Check system for proper operation.

Sorry that the drawings don't copy correctly from the manual.

 

[dcurtis]

I read that exact write up on the orifice tube, any ways I took the one that the last owners had installed in to the other line, think it was the high pressure line and removed it and then recharged the system, air was cold as can be so I stomped the throttle and no more blow off, I'm guessing the extra orifice tube it the wrong line was building the extra pressure, but it's gone now and my ac works like a champ now, to think 5 minutes worth of work could have saved me from about a year of having no A/C, oh well it works now, and I know something about ac's aswell. Thanks for the help.