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Old 08-16-2005, 11:06 AM
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Expansion Valve Tweaking

Has anyone heard of tweaking the expansion valve. Open or close it more?
They're spring loaded so I'm not sure it can even be done effectively. I've taken a couple of them out and disassemble them and cleaned them. Back to normal. But could they be better?
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Old 08-16-2005, 11:13 AM
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I've never done it, but once knew the owner of an independent garage who claimed that he could get 36F vent air from auto a/c systems by "tweaking" the expansion valve and not freeze up the evaporator.

There are those who know and there are those who know more.

Interesting subject.
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Old 08-16-2005, 03:54 PM
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well, I took one of my old xpansion valves and installed it with a modification. It didn't freeze my evaporator but it did not help performance yet. My garage man said to run it a couple of days.

Before the change I was operating at a low high side pressure 25-30; and the hose exiting the evaporator was minor cool; almost lukewarm, must have been good heat transfer in the evaporator and car would cool ok. Also, the line into the evaporator was NOT Hot to touch at all.

With the modification to let more "liquid gas" into the evaporator; I now have a hot to touch line into the evaporator and still a lukewarm exit hose from the evaporator; a high pressure of 65 and not much cooling; maybe less than before. I will remove the valve and check to see if it is still the way I modified it.

I'm getting flow through the drier; yet it is cloudy. I am experimenting with brute force and maybe I'll get lucky. If not, I'll still use the stock setting, but I just have to know.
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Old 08-16-2005, 05:16 PM
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You need to become VERY familiar with what "superheat" is; and how to measure it, if you are going to play with the TXV.

You're going to "SLUG" (or have slugged) your compressor. 65psi high side means refrigerant is running right thru.
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Old 08-16-2005, 07:06 PM
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I must admit, i've used superheated steam but i know absolutely nothing about AC. I was just thinking about the xpansion valve being a conduit for the liquid to turn into the gas and become cool very quickly. That is not happening to my system right now with the mod. I might have too much oil in the system, since I have emptied and recharged about 3 times now. Each time 2oz. oil is added. I did fail to mention that this last time I flushed the condenser and evaporator just because it was there; air shop hosed it out the best I could, but I know some of that is in there too. I tend to think that I have a restriction in the xpansion valve or that I have too much oil in the system. It was running half decent before. But not what I want. I want to try to "freeze" that evaporator....thought I was on the right track.
It's my holy grail
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Old 08-18-2005, 09:50 PM
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No, refridgerant was not passing right thru; there was a restriction in the txv. I want "low superheat" living dangerously; coldest near to the end of the evaporator; a cooler exit line like a cadillace (they use txv too) yes refridgerant can leak through and slug the compressor. But I think there may be more room to play with than we think.
Why are some GM cars spec'd out for desert settings txv? I think one size does not fit all. I am sacrificing my time and may have to sacrifice a compressor eventually, but I think this is very valuble information.
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