A/C Orifice Tube Replacement

[85Dave]

I suspect that the orifice tube on my 92 is plugged. The low side pressure with the compressor running is 80-100 psi. I just changed over from R-12 to R-134a. I added 2 cans of 134, and the A/C worked OK for 2-3 days. Then the compressor started short cycling, and now it only comes on for 1-2 seconds upon startup.

I depressed the shrader valve on the low side, a little gas came out, and pressure went to 0 psi. I momentarily depressed the shrader on the high side, and gas came out with great gusto. So the high side is really high right now. After sitting a few minutes, the low side (engine off) went to over 70 psi.

So I'm guessing that the orifice tube must be plugged. What is involved with replacing it? Does the accumulator have to come out?

 

[MyExpWork]

Do a search on "A/C" or some combination. Several useful threads will show up, including one with pictures and a writepu on how to replace the tube.

Good luck.

Brian

 

[85Dave]

I did a search on "orifice", and found lots of info, but nothing on how to replace it. Did I miss something?

 

[MrShorty]

It isn't too bad. The orifice sits at the junction of the liquid line from the condenser to the evaporator and line going into the evaporator. You'll need to get the system evacuated. Then disconnect the liquid line and the evaporator. This union is below the accumulator near the bottom of the evaporator housing. The hardest part here is getting at it, and I found it easiest to come from below. Once disconnected, use the special orifice tube removal tool (can be borrowed from autozone) to pull the old orifice tube out. Put the new one in and reconnect.
Because Ford AC systems are know for what is called "the black death" (a build up of black crud that can clog off everything) while you have the system evacuated and open, it might be a good idea to flush the whole system out (evaporator, condenser, tubing) and make sure it is clean.

 

[TPLYNCH]

Search for V8boatbuilder (?) he did an A/C writeup with pics fairly recently I believe..

 

[Glacier991]

This thread may help you. It also contains a link to the article with pix posted by V8Boatbuilder.

http://www.explorerforum.com/forums/showthread.php?s=&threadid=77331


Happy Exploring

Chris

 

[85Dave]

Thanks for the links, guys. After doing some more research, I suspect that my 92 experienced Black Death about 3 years ago when I replaced the compressor and accumulator.

Here's my game plan:

Disassemble system. Flush condenser until clear. Will use lacquer thinner.
Flush suction/discharge line.
Replace liquid line.
Replace orifice tube.
Replace accumulator.
Evacuate system.
Re-charge with 2 cans of 134a that has oil in it.
Cross fingers.

Any other thought/advice? What about the variable orifice valves? Do you think the compressor will be OK as is?

 

[Glacier991]

I'm not keen on the lacquer thinner flush part, but if you do, follow up with an Ester based flush, and use ester based flush on everything else. If the orifice valve is crudded up when you pull it, I would probably recommend compressor replacement. Otherwise your plan sounds fine. Oh, some folks would recommend reverse flushing the evaporator. And check system capacity... 2 cans ain;t gonna do it. Save your S on refrigerant with oil in it and add it to the compressor and accumulator when you replace them. I'll check your system capacities and post it in the next post.

Happy Exploring.

Chris

 

[Glacier991]

System capacity for oil is 7 oz. You may get by with 6 is it comes in a 6 oz container. use PAG oil. If you replace any hoses make sure they are "barrier hoses" or else run mineral oil through them and let them sit over night, flush them and THEN use them (sounds dumb but trust me - chemistry). Refrigerant capacity is 32 oz R-12 but you will need less R-134a... 90% of the R-12 charge, so two cans of 14oz SHOULD do it (I stand corrected). Don't buy oil mixed with the rerigerant, no need. Just buy straight PAG oil, put a couple oz in the accumulator, a couple oz in the condensor and a couple oz in the compressor, and you'll be set. How do you plan to evacuate it?

Happy Exploring

Chris

 

[85Dave]

I have a friend that will lend me an electric vacuum pump and a set of A/C gauges.

About your suggestion of replacing the compressor if the orifice is dirty, I replaced the compressor and accumulator about 2 or 3 years ago. It seems to be working OK. Do you think the Black Death goo could have messed it up?

 

[85Dave]

Also, what exactly is an ester flush? And where can I get it? Autozone, NAPA, etc.

 

[Glacier991]

Dave... when you pull the orifice valve, if it is plugged with black crud you have a decision to make. Do you HAVE to replace the compressor ? Well, maybe not, but do you want to risk another imminent failure with more component replacements, or bite the bullet and be safe and replace? Commercially it would be replaced to avoid a come back. Do you absolutely have to? Hmmm, your call.

Autozone of any other place that carries AC stuff should carry "AC flush". They carry the ester kind.

When you evacuate, let the pump run for at least 30 minutes or so. It will appear to be evacuated in just a few, but you need time for the molecules of moisture to migrate out. With real sensitive equipment you can see the vacuum continue to progress over 30 minutes (or longer). Trust me on this one.

You should do fine. You might want to follow V8's lead and submits an article with photos. You are doing the conversion correctly (this time).

Happy exploring

Chris

 

[85Dave]

Chris,
Thanks so much for your help.

I pulled the orifice tube, and it did have metal shavings and black crud on it. But I believe that it is from the previous compressor failure. I didn't flush anything last time, and this is probably just the leftovers. The "new" compressor has 50,000 miles on it. The original one had over 100,000. Yesterday, it was putting out enough pressure to trip the A/C high pressure cutoff switch. So I think I'll take a chance and not replace it right now. Wish me luck.

I flushed the condenser, liquid line, and back flushed the evaporator with paint reducer ( mild version of lacquer thinner). The oil came out dark, then clear. Very few particles from the condenser. I used an empty, clean 1 qt. gear oil bottle. The tip was just the right size to go into the lines, and by squeezing the bottle, I could force the reducer through. I then followed with a flush of rubbing alcohol, then compressed air.

Tomorrow I'll get the A/C flush and use it just to be sure. Then I'll replace the orifice tube, accumulator, and all o-rings. Re-assemble and evacuate overnight.

I don't have a digital camera, but that would be a great idea. Thanks again!

-Dave

 

[Glacier991]

Good going Dave. I should have mentioned you should use the green O-rings. If you HAVE to use black ones, soak them in mineral oil pre-assembly. (I know you are wondering, but the deal on mineral oil is this... 134a won't carry it, but the small molecules of 134a also cannot get through it either. If you took two new hoses, neither one "barrier" (eg designed to contain the smaller molecules of 134) put mineral oil in one, and not the other, the mineral oil hose becomes more or less "barrier" in the process. Same with O-rings. I usually use green o-rings though, and use an assembly lube/sealant called NYLOG. leaks are a thing of the past on o rings for me.

Oh and <smile> Good luck on the compressor.

Happy Exploring

Chris

 

[Glacier991]

One more thing. When you use the manifold, you will hook a hose to high and low sides, and the center hose to the vacuum pump. When you are ready to shut down the pump, close both high and low sides on the manifold (of course) and before the pump is turned off, unscrew the fitting on the hose at the pump, til it leaks, THEN shut off the pump. When you hook up the refrigerant can, (all hoses nice and tight of course, open the valve, and then unscrew the hose to the can at the manifold, allowing a little refrigerant to escape, purging maximally any air in the hose or manifold. Then tighten it back up, turn the can UPSIDE DOWN and open the high side valve. The vacuum in the system should suck in the entire can. Close everything back up, attach the new can, and repeat the purge procedure, then upside down into the high side until it won't take any more. Close everything back up, start the car and turn on the air. It should run on what's in it. now, with the can RIGHT SIDE UP !!! open the low side valve, and allow the rest to go in as a gas to be compressed by the compressor.

HTH.

Happy Exploring

Chris

 

[85Dave]

Thanks for the tips, Chris. I just got the vacuum pump, and I'm on my way to get the gauge manifold. The vacuum pump is designed to run 24/7, so I'll let it run all night. Hopefully, tomorrow morning I'll have cold air, and my Taurus back. Wifey commandeered the Taurus until A/C is fixed on the X. But in the meantime, I'll just enjoy driving the back-up car, 1985 Corvette!