Background: Failing AC system in western suburb of Chicago. Unit is 22 years old, Carrier 2 ton w/gas furnace 70k btu.
I had a tech out today to look at my AC and give me an estimate on replacing the system with a high-efficiency system and be eligible for gov. rebate. He gave me several options, but the last option was that he could probably fix the existing unit by just replacing the Schrader valves for $2-250. He said that if the unit is freezing up that it is still operational and had some life left in it.
What is the opinion and/or success rate on replacing the Schrader valves.
If it's leaking Schrader valves, the success is nearly 100%
They even make a tool for replacing them.
Here's the tool:
or
These allow you to remove the valve core, put in a new one.. and you hardly loose any refrigerant.
But.. if it's just a slow leak.. and the unit is on it's last legs, a "cap" over the Schrader valve will seal the valve, after the unit has been re-charged.. and the cap has a rubber gasket which will keep the unit from leaking.
It will be hard to service, in that, when you open the cap you will loose a small amount of refrigerant.. but, unless the valve is completely shot, they usually just leak a little.. (In fact every one of them I've ever seen, leaked a little.. it's just "does it leak so much that you can't get a cap on it in time to preserve the charge.
Your suggestion of using a cap with a rubber O-ring is right on. I paid a serviceman hundreds of dollars to find a leak on my unit, only to discover the leak was at the Schrader valve. It was solved by the cap and held a charge for years after installing it. To say that I was upset with the technician's performance would be the understatement of the year. Yes he did have a sniffer for detecting Freon, and one would have thought that would have been the first place he would have used it. It is incidents like this that make people suspicious of servicemen for their HVAC units.
Everybody has their "priority list" based on their own experience with various types of systems.
He's got a truck load of gear, and probably several years of experience.. and he probably searches in an order that he has found has worked in the past.
Some machines are more prone to particular types of failures than others.
Usually, when you pull the service caps off you get a quick whiff of freon.. they all leak a bit.
Now.. if somebody serviced the machine and didn't put the caps back, then that's the first place I'd look! And.. it's one of the first places the tech goes, 'cus he needs to hook up his gage set to see what's going on.
Usually all he's got is a vague "It doesn't cool well any more, or it freezes up".. as a symptom.
He's got to start someplace.
It's about like the computer tech that shows up, to a problem that has baffled folks for weeks.
He walks in, checks a couple of things.. gives the machine a swift kick.. and hands them a bill for $10,000.00..
They all balk at the bill.
So.. he re-writes the bill.
Diagnosis. $200.00 Application of corrective action. $10.00 Knowing where and how hard to kick $10,000.00
I can appreciate your explanation, but after two years of trouble shooting, one would think the first place a person would look for a leak is where the Freon is inserted. I could tell you many more stories about HVAC techs, but I am sure you do not want to hear them.
The tech also started to talk about the fact that some times the leak is in the copper lines running under the slab, and if so you have to cut a lot o f concrete to install new lines. He recovered and stated that the leak is a lmost always at the Schrader valves. Do you every find that the copper tube s fail ?
What about cleaning the tubes ? Some techs talking about cleaning and other s talk about just evacuating them does a better job ?
There are hacks in every profession.. and some outright crooks sprinkled in for good measure.
A schrader valve under a good cap wouldn't be too high on my list, because the cap would stop a leak there.. and because, since every schrader valve leaks a tiny amount.. sniffing right after you pull the cap will almost always show a whiff.. but that's only because the small amount that leaks by the valve is trapped under the cap.
And when a service hose is on the valve, it's "open". So... getting some right after you pull the hose is a high possibility.. but it still doesn't indicate the source of a "leak".
I use a cleaning fluid sucked in with a vacuum pump then blown out with dry nitrogen. Back in the good old days you could use R11 to clean out a system but these days we must protect the cute fuzzy little ozones. After cleaning out the condenser, evaporator and line set, I do a triple vacuum on the system after determining there are no leaks then recharge it and start it up. If it's done right you'll never have a failure due to contamination. Of course make sure there is enough oil in the system. ^_^
Oh hell, I forgot a small bottle of acid neutralized added to the compressor oil as insurance. It will neutralize any acid that may have been trapped in the system. ^_^
Hi, I spent all my working career as a support specialist for things field techs couldn't figure out or handle(not in HVAC field). Years of dealing with them worst techs are those who approach problems based on past experience rather than looking at it as brand new first time seen problem. This type of techs never improve themselves. Waste lots of time and cause lots of trouble for other fellow techs including those like me.
A good field service tech is a mix of skills... Observation being the most key.
And fresh eyes always help.. When you have been looking at a problem too long you can get into the mode of "I've already checked that, it can't be..."
Some techs can "cookbook" themselves thru a problem, and, when they have replaced enough parts, the system is functional again.. but often there are a pile of good parts that have been replaced, needlessly.
If those lines are touching that concrete slab...you may also have a flash gas problem. cleaning the fins on the condenser and the evaporator is just standard good annual(or more) practices. Perhaps it is time for you to renew that system anyway. The cost of R22 and its availability is rapidly putting it on the endangered species list. The new cooling gases and the higher efficiency systems may well be your best bet.
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