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Discussion Starter · #1 ·
I have a 99 ZX2 and the A/C recently started blowing ambient temperature air. I'm trying to locate the problem and need some help since it's not one of the usual suspects of A/C problems.

Things I know aren't the problem:
  1. A/C compressor, it's cycling and building pressure just like it should be
  2. Freon, I have a gauge it's well within the expected pressure range
  3. Blend door, the blend door is mechanical, so I can hear it moving and it definitely shuts off the hot air when I turn it to cold
  4. Any switches (pressure switches, CCRM, etc), as I said above, the compressor is running and cycling on and off just like it should
Where I suspect the problem is:
I measured the temperature of the lines in various places with an infrared thermometer after running the A/C for about 5 minutes. The high pressure lines (liquid line) right off the compressor gets up to about 135F and as labeled below in the picture, before the condenser it's about 115F, after the condenser is about 90F. All of this seems pretty normal to me at this point. But right before and after the hood switch, there's a huge temperature difference. Then by the strut tower it's starting to warm back up again. The low pressure lines on the other side of the car are whatever temperature the engine bay is.
Motor vehicle Hood Automotive tire Automotive exterior Auto part


Given all this, I suspect there's some sort of blockage and the Freon is decompressing (and cooling) before it should. Then it warms back up to normal air temperature by the time it gets to the evaporator. I took this apart once and found just inside the stainless colored line was this.
Hood Automotive tire Automotive lighting Motor vehicle Tread

(Sorry about the blurry picture). There's a vertical bar and a steel ball of some sort that appeared to be mounted in there, so I assume they're supposed to be there. This is where my knowledge of A/C runs out. There was also some foreign material in there, which you can barely see around the edges. I blew this out with my air compressor at 120 psi in both directions, which I thought did the trick but I still have the same problem.

My questions are:
  1. Does anyone know if that bar and ball are supposed to be there and what they do?
  2. Is it likely there's some sort of a blockage in that line I need to get cleared out?
  3. What else could it be?
I haven't been able to find this line anywhere (except RockAuto but the picture doesn't match the shape of this line so I don't really want to buy it just yet). I don't think there's much of a chance of replacing it.

Thank you for your help.
 

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That is the expansion valve. you should be able to pull it out with a pair of needle nose. note the color of the valve represents the orifice diameter
 

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Discussion Starter · #3 ·
That is the expansion valve. you should be able to pull it out with a pair of needle nose. note the color of the valve represents the orifice diameter
I did some searching around, it seems like this is more commonly referred to as an "orifice tube" and is used in place of a true expansion valve? What I've also noticed is that none of the orifice tubes on Autozone's website and others don't look like the one that is in the car currently, which has me a bit confused yet.

Example orifice tube at Autozone.
 

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yes. the reference is correct.. orifice tube is the modern nomenclature for expansion valve.. same principle. next thing... forget autozone completely. delete that from your memory. the 'orifice tubes' are all pretty much universally accepted by color. so once you get it out, clean it up and figure out what color it is. then you can look for the proper part. NEVER waste your time at autozone. thats like going to a proctologist for ankle pain. orileys carries these parts in almost every store. but you must know the color. its probably either blue, orange or white.
 

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For diagnostic purposes I find it helpful to drive around with something like this in my center vent:

https://www.amazon.com/Supco-ST02-Stainless-Thermometer-Degrees/dp/B003CL9LMC/






Another data point to use is with the engine off long enough for the pressure to equalize (like not having drive the car for the day and above 60 degrees F) check the low side pressure and report back.

This chart will tell you if refrigerant is in the proverbial ballpark:
 

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Discussion Starter · #8 ·
yes. the reference is correct.. orifice tube is the modern nomenclature for expansion valve.. same principle. next thing... forget autozone completely. delete that from your memory. the 'orifice tubes' are all pretty much universally accepted by color. so once you get it out, clean it up and figure out what color it is. then you can look for the proper part. NEVER waste your time at autozone. thats like going to a proctologist for ankle pain. orileys carries these parts in almost every store. but you must know the color. its probably either blue, orange or white.
Thanks for confirming the orifice tube for me. Learn something new everyday. It must plugged up for one reason or another.

Also thanks for the unwanted advice on parts stores. I'm sorry your experience with Autozone hasn't been great but I've gotten a number of parts for free due to their warranty program which I have yet to see O'Reilly's match. Nothing against O'Reilly's, I buy things from there too and frankly I don't care where I go if they have the part I need.
 

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best thing I have found is that I would rather not use the warranty, and get a higher quality part to start with. I spend about 5k a month with orileys and have never been left up the creek, but I also have commercial accounts. They pay me labor claims too if something fails. For your average user maybe AZ is fine, but over the years I have seen more junk parts from them than anyone.
 

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If the orifice tube is plugged up then it's likely that you have had a compressor failure and the whole system needs to be flushed and the compressor replaced. Do you have any pics of the orifice tube that you pulled out? If there is a blockage then it should be fairly visible. What I find strange though is that you say the pressures were where they are supposed to be which would be the case of there was a blockage. There is also supposed to be a temperature shift at the location you noted, it's normal.
 

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so now that you have opened the system the real test can be done.
put some of the dye oil in it then put the system back together. You can just put the oil in the open part you have. Be sure to clean it up after connecting the line so it does not show up under the light and mistake it for a leak if it is not a leak.

vacuum out the system. 99 zx2 is supposed to take 1lb 8 oz of refrigerant. This would equal 2 cans. I would not put two cans into it to start it. I would start with one. One can will activate the sensors and get the compressor going to draw in the first can. It should be enough for it to cycle while it is idling. I would let it cycle for about half an hour to ensure the oil has circulated in the system. Then I would use the light at all the connections and look for a leak

if there is no leak then i would proceed to put in the other can and stop at around the 10oz mark. Slightly underfilled will still work fine and get the temps in the mid 30s. Too much will cause the system to shut off or even freeze up and shut off.

post a pic of the vacuum unit you are using so i can follow up on this and be informed for further assistance
 
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