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How do i install an A/C orfice tube

mo5005

Member
Joined
Nov 18, 2007
Location
California
1324829.JPG
http://www.fcpgroton.com/images/products/large/1324829.JPG

I just slide it into the high side of the evaporator. Is it really that easy?

1988 Volvo 760 T 190K.
 
If it's in the evaporator then yes it's that easy. They are in different places on different models. The last 740 I owned it was in the evaporator. My 940's is in the evaporators supply pipe and is a bit irritating to get to.

You will also need a new seal for that connection and some refrigerant oil to lube the seal. Once the orfice tube is installed you'll need to pull a vac on the system to test for leaks and remove any water vapor that gets into the system while it's open.

Later,
Stephen
 
1324829.JPG
http://www.fcpgroton.com/images/products/large/1324829.JPG

I just slide it into the high side of the evaporator. Is it really that easy?

1988 Volvo 760 T 190K.

On your car the orifice tube is inserted into the high pressure line at the firewall on the engine compartment side, in the fitting. Just purge the system, remove the compression fitting nut, remove & replace the tube.
Take a good look at it. If it's full of black crud, there's something wrong with the system components.
Well it's not really that easy. If you really need an orifice tube, then system needs to be flushed, and components checked for breakdown, parts replaced, seals repalced. A good flush menas removing every fitting and rinsing each hose & component, except the pump. Then purging the system to remove vapors, and check for leaks. The pump is the source of the black crud in the lines, so if it exists, a new compressor is needed usually.

Oh if you are looking at the 'adjustable orifice tube' that FCP Groton sells for $25, don't get it. IMHO, the adjsutable tube gets clogged much more frequently than a regular $1.85 one, especially on an old system that has had it's share of bad compressors, dryers, and crud. Once the tiny adjustable orifice is clogged, even a little bit, the system over-pressures and vents all that expensive refrigerant out the safety valve. I was warned by the experts, put on in and regretted it. I ended up with the std tube, and doing the job twice.
 
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holy crap that thing happened to me last summer. (purge of gas out the safety valve) i thought i had a clog. i did check the orifice tube for metal debris and crud.... but it was clean. i'm about to fill my AC and now im worried about having that adjustable orfice tube.....anyone else have any opinions on these "adjustable orifice tubes?"
 
my 25.00 tube works great, from napa. it's the 4 seasons one i think. fit it right on the framerail junction. flush/vacuum the system out, new o-rings, and a full charge and mine gets to like 34 or something at the vent. whatever it is, it's really cold.
 
I've got one installed currently. It was stuck the first time I started the A/C this year. It has since worked loose and is behaving properly. The system in my 940 has never bled freon. It will cycle on and off when the VOV is stuck in the (I'm assuming closed) state. I assume the 940's have a high pressure shut off switch. The VOV worked perfectly the first season it was installed. It really helped in city cooling.

I'm planing on removing the stuck VOV in a week or two. I haven't decided if its getting replaced with another VOV or a fixed orfice tube. Either way the system is getting recharged with DuraCool.

Later,
Stephen
 
so if the variable orifice valve get stuck "closed" your AC system will run crap since no refrigerant is getting to the other side of the evaporator?
 
so if the variable orifice valve get stuck "closed" your AC system will run crap since no refrigerant is getting to the other side of the evaporator?

Correct, however "closed" is the wrong term. What actually happens is the VOV is stuck in it's smallest orifice size. It will cool ok at idle, which is what it's designed to do. But as engine RPM's come up the compressor will start to cut in and out because of high head pressure. Like I said, mine will work loose after 30 - 60 seconds but I'm still gonna change it.

Later,
Stephen
 
which side goes into the evaporator..... i just vented another 2lbs of refrigerant out the back of the compressor..... so im seeing if i mistakenly put it in wrong.
 
okay. i did that right.


is there a possibility that the compressor overpressure valve is just opening up at a low pressure?

and if so.... how do i replace this valve?
 
i have no idea. it only vents when it gets hot outside. The way i charge the system is:
1. Pull a vaccuum for 1 hour
2. Then put in 2 lbs of refrigent while the car is cycling the compressor.

(I do have the AC gauges.... but it never vents when they are on)
 
On my car, when charging the high pressure side went up to way over the red line on my gage one time i did the charge, and dumped only a 1/2 can before I stopped. At other times, it was fine until I started driving for a while. Once the gage kept well below the pressure level and 'spiked' all of a sudden, then went back to normal pressure, which is something I attribute to the adjustable orifice doing funny things.

When you charge it, do it very slowly with gage connected, and look for the pressure to stablize as it fills. If you have one of those cheap fill set-ups that you get at the auto parts stores, you may want to get a fill manifold that measures both the high & low side pressures while filling, as the cheap gages don't respond quickly and are not very accurate.

Also, the system when converted to R134 takes about 20% less refridgerant that R12, which is 2.2 lbs IIRC for the 240, and should be 1.8 lbs, and 2 lbs is overfilling the system. It will cool better when not over filed
 
i switched back to the fixed orficie valve. I do have a set that measures both high and low.... the problem is that i cant measure the high side since the connection port is too close to the chasis wall and the AC gauge cannot fit there. I checked on the brickboard and since i have an 88 760 charging it to 2.0lbs (900 grams) is not overfilling it. I just so stumped on why the AC will work perfectly (blow below freezing) at the vents and then as soon as it gets alittle warmer (75+) it will vent.

Is it a possibility that the compressor is at fault?
 
When you first changed the orifice tube and flushed the ssytem, was it full of black crud?
If yes, then the compressor could be on the way out.
Also, if the system is otehrwise ok and not clogged, then two possible things could cause the pressure to rise and vent, one is that the aux cooling fan on the condener is not working, and two, the condenser itself is not doing enough heat exchange, and is still full of crud.
 
my 25.00 tube works great, from napa. it's the 4 seasons one i think. fit it right on the framerail junction. flush/vacuum the system out, new o-rings, and a full charge and mine gets to like 34 or something at the vent. whatever it is, it's really cold.
+1 I had one fitted to my wife's S70 last summer. It has worked faultlessly in the Alabama heat - mind you the compressor was replaced too and it was professionally installed by a reputable Indie Volvo shop.
 
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