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!
Justin

Before I start, check this site to give you the basics on A/C.

By the way, I am of old school and TXV and TEV are the same thing.

A/C

Now, at least, we are starting on the same page. For more information, check for a book at your local library.

I can not support or deny his diagnostic of your unit. There are a lot of things to consider. Possible, yes.

TEV, thermostatic expansion valves modulate the amount of refrigerant flowing to the evaporator by means of a bulb attached to the Suction Line as it leaves the evaporator. As the temperature rises at that point, it puts pressure against a spring and opens the valve a little more and allows more refrigerant in. As it senses the cooling effect of this, it modulates a little closed. The only failure of this device I have seen on my 30+ years in the trades is if the small tube that connect the bulb to the valve gets cracked or broken and it can not inflict pressure on the TEV to open it. It fails closed do to spring pressure.

I have seen something that would cause the TEV to block up but there were other problems that caused that.

Checking the TEV is most simple for a QUALIFIED service person to do.

Before one can check the system, one has to put on a set of gauges. This is how we check the refrigeration circuit for possible trouble.

This is kind of like the doctor checking you blood pressure.

If the expansion valve is bad, he would see a high pressure on the high side of the unit and this may even be normal pressure. The low side would be vary low even in to a vacuum as to compressor try to put the Freon back to it.

Normal operating pressures for R-22, the refrigerant used in older units would be around 200 psig on the high side and 60 psig on the low. (psig= pounds per square inch gauge)

I am a little surprised that you have an expansion valve on you system. These are a little expensive and cheaper devices can be used. I am wondering it this is a “Heat Pump” unit.

As far as you checking anything, unless you are there with him and he will explain what he sees, you under his control. You need the tools and training to use them. You have to trust him. This is why there are so many unscrupulous service people out there. They can tell you your widget is broken and you have to believe them.

$400 to change out the TEV is about right. The EPA has made it mandatory that we do it according to Hoyle. No refrigerant may escape to the atmosphere. This drives the cost up as it is all labor and time.

Besides, he probably is on commision. Another thing I hate. Sell, Sell, Sell. Get that bonus.

Try to find a recommended contractor. Watch what he is doing. Have him explain what he sees and then, get a second opinion.

The bottom line is there are not cheap and quick fixes to a broken part.

I have a little retirement business giving second openions. You know you can trust me as am not there to sell you anything. For $50 for an hour of testing, I will check your system out and give you the honest poop. Then you have to find someone to fix it. In your case, that's 50 plus expenses.

At 50 bucks I am not going to get rich but I get the satisfaction that no one can pull the wool over my customers eyes.

Welcome to the Pool and hope you get the wife cooled down soon.

WoW

Thanks for the reply. It is a pretty new system and yes, it is a "heat pump" system. I didn't immediately think the guy was dishonest, its just $400 is alot and I wanted to be sure. He also wanted to charge my wife labor because I had removed the panels for him to get access as a courtesy (very easy removal). There was eight screws and he was trying to charge her labor to put them back in. That seemed a bit off to me since the cordless drill with the correct bit attached was sitting right there for him to use. He did indeed install the panels with the drill after I talked to him over the phone and did not charge labor. I am just weary sometimes, especially when your wife is home alone. You never know who you can trust, and women are usually the victims. I was reading that ice should form prior to the TEV but there is no ice and it only feels slightly cool when the whole system is running. I will check the bulb. I also read immersing the bulb in hot water could be a fix, thats why I was thinking of the blow dryer idea. Since I cannot remove it to immerse it in water I would just try the blow dryer...dumb idea? ok, thank you for the help.

One way we use just to check the TEV is to immerse the bulb in water. This will not fix the problem but has been know to clear it if it got blocked with wax. That's another story.

If he knew what he was talking about, he would not just think it was the TEV, he would know.

The small copper tube feeding refrigerant should be slightly warm to warm. Normal operating temperature at this point is around 90-110 depending outside temp and how far from the outside unit.

The other side of the TEV should be 35 to 45 degs. If you did have ice there, that is one of the signs that there COULD be a problem with the TEV. Further tests would be in order. Normally, only the power top on the TEV needs to be replaced but on inexpensive home unit, this may not be possible.

On an A/C unit, there should never be ice anywhere. That is a definite sign of a problem. From dirty filters to low on charge.

I wish I was there to "Lay Hands" on it to give you better help.

Now on a funny note, me fees are:

$ 50 per for a good guess
$100 per if you tried to fix it before calling me.

Good Luck