Expansion Valve Stuck Closed - HVAC - DIY Chatroom Home Improvement Forum

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Old 08-30-2007, 10:28 PM   #1
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Expansion Valve Stuck Closed

Our Central A/C has been blowing warm air for about the past week or so. I have tested with a new thermostat, completely cleaned the outside unit, cleaned the evaporator coils/fins, and tested continuity and voltage on the wiring harnesses. All components appear to be running properly, although I have very little knowledge of A/C systems. I finally decided to fork out the cash for a service call and the technician came to the conclusion that the Expansion Valve was "stuck" in the closed position. The system is still under a limited warranty for parts and he offered to replace the valve for a fee of approximately $400 for labor costs. That price instantly raised a red-flag for me so I declined, paid him the standard service call fee and sent him on his way. Like I said before, I have little knowledge of A/C systems but I felt the small service call fee was reasonable to be cautionary and do some researching first. Since I am a Navy Aviation Electronics Tech, it is my nature to at least attempt a fix on my own with as little resources and money as possible; we're no strangers to launching F/A 18's into the sky with duct-taped wings (just kidding...just kidding). So after doing some extensive searching on the internet for my problem I am still at a dead-end. I have read opinions that many techs can falsely diagnose the TXV as probable cause of failure. Apparently the indications of a faulty TXV are similar to other components (sensor bulb, among others, whatever this is). So I am seeking a possible "quick-fix" solution until I can afford to replace the component or even a solution that can fix it permanently without having to pay someone to evacuate the system and replace the valve. Is there any "myths" out there I can try? I'm thinking in terms of the potato to remove a broken light bulb theory or toothpaste to repair a scratched CD type of theories. I was thinking about turning the heat on for about an hour, or even turning the A/C on and blowing on the valve with a hair dryer or something. I am pretty desperate. Please help if you can, I am in TX and my wife and kids are starting to get cranky and it is dangerously hot this time of year.
Thanks in advance!


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Old 08-31-2007, 03:42 PM   #2
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The TXV is strictly for pros to mess with. what you can do is make sure the sensing bulb is secured to the suction line. I think you should have had them fix it . to come back should cost more money


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Old 08-31-2007, 04:49 PM   #3
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The expansion valve may be installed two ways. Soldered in or secured with chatleff (sp?) fittings. The unit will need to be pumped down, this can be done by pumping it into the condenser, old valve removed and new one replaced. Then the system will need to be pulled into a vacuum and the refrigerant dumped back in. It's about a two hour job on the average.

One symtum is low suction pressure and high discharge pressure.

Other than hand tools, you'll need torch and rod, vacuum pump, refrigerant and of course, the new valve.

Warranty work around here for the job is around the $200-300.00 with the valve swapped out by the distibutor.

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Old 08-31-2007, 04:59 PM   #4
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I have seen a lot of these misdiagnosed. One time a tech replaced the valve 3 times on a brand new construction unit. Yes, he actually replaced it 3 times. He thought he kept burning the new valve up whenever he brazed it in. I went out there with him one day and found out that the installers severely kinked the suction line behind the wall. I have also went behind people and have found misdiagnosed TXV's and the problems ranged from clogged liquid line filter driers to the system being low on refrigerant. There is a good chance that it is a misdiagnoses. Unfortunately, it isn't a do it yourself project. It would cost you more to buy all the tools than to have it changed out. I would hire another company to take a look at it and go in there blind. Do not tell him that a guy diagnosed it as the TXV.

Last edited by Malcolm; 08-31-2007 at 05:03 PM.
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