A/C question: can't measure freon pressure???

I'm having problems with my A/C unit. A service technician came to my house, looked at the compressor unit, and told me the panels were full of debris that he couldn't accurately measure the freon pressure. He asked to clean the panel for $89, which did not include the service call, another $79.
I just don't see the connection between the cleaniness of the panels and measuring the freon pressue. Isn't freon inside copper tubings? What does it have to do with the panels? Is this guy trying to rip me off?
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John Smith wrote:

If by "panels" you are trying to describe the finned outside condenser coils or the evaporator coils in the air handler, then he wasn't jerking you around.
The freon pressure depends on several things, and one of them is thetemprature it's at at various points in the system, which in turn depends on the ability of air to move over those "panels" and carry heat away from the condenser or warm the evaporator.
To be meaningful, pressure readings have to be made with the equipment running in a "normal" condition, not an abnormal one where air can't flow as freely as originally intended.
Capice?
Jeff
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Jeffry Wisnia
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Jeff Wisnia wrote:

You can clean out the coils yourself with a water hose...
this just might fix the problem..
If the airflow through the coil is restricted the coil temperature will be high and the freon pressure will be high.
by the way...what is the problem?
Mark
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Mark wrote:
<snipped>

But not as well as you can by spraying them with one of the many available coil cleaners which help disolve grease and muck.
Some cleaners are more acidic than others and can cause problems if they splash on the user's skin or nearby foilage.
It's sort of like the difference between cleaning a greasy frying pan with plain water versus water and detergent.
Jeff
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Mark wrote:

Temperature won't get below 76 oF.
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Dirty coils are sometimes the problem. Call the man back.
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Christopher A. Young
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John Smith writes:

No, these guys don't rip you off for $89. Why should they when they can rip you off for $1000s?
Let's assume you really had the clogged coils that would result in distorted pressure readings, and cleaning was in fact a necessary first step in diagnosing your performance problem.
He's asking for $89 to perform what is essentially a small maid service. A little thinking and effort on your part could have diagnosed this on your own for $0, and so you are probably not very knowledgeable and will have no resistance to technical points of selling. It would have been more reasonable for him to say, "you can pay me to clean it, or you can do it yourself, and then I'll come back." You did pay him for a service call and initial diagnosis, and that is the initial diagnosis. Curious that this cleaning is about the cost of a 2nd service call.
It is also possible he is testing you. If you will pay $79 + $89 for some cleaning, then you are a good prospect to fall for the $1000s it will cost to replace your system unnecessarily. Otherwise he's looking at a resistant customer who isn't worth pursuing for repairs *or* replacements. For your $79 you got directed to your own owner's manual.
Most shops seem to be in the R+R biz (remove and replace), not the D+R biz (diagnose and repair). And why not? The former takes less brains and makes more money. The D+R front is just a way to get their foot in the door first, and soften you up for the R+R sales pitch. If you have a 7-year-old system that could be repaired to last 15 or 20 years, they'll tell you that a new system will save you all kinds of money on "efficiency," which is a comparison of your malfunctioning old system to their over-optimistic specifications on their new.
The 1st defense is to know the technology yourself. You have to be somewhat knowledgeable of diagnosis yourself, to avoid being fooled by a purported diagnostician.
The 2nd defense, if you can't manage the 1st, is to invite and 2nd tradesman out, and challenge him to prove the 1st guy wrong. Competent and honest diagnosticians love to do that, versus, R+R salesman who will assume the 1st guy's death sentence is fact and launch into a sales pitch for a new system.
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If the coils (the tube and fin assemblies) are dirty, you can still measure the freon pressure. Just takes a set of gages. However, the pressures won't accurately tell much about the system.
Clean the coils, and you'll get a lot more useful information. And your system may well start working again.
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