Heat Pump repair, am I getting hosed?

My heat pump has never been all that great, but near the end of winter (here) it pretty much stopped working altogether. Here's the back- story:
My house is about 1700 sq.ft (heated), and has a single heat pump. I'm not sure what size it is, but it's a Bryant, and I'm wanting to say 3- ton. It was installed in 2000.
It has worked fine until about 4 months ago, when we noticed a ridiculously high power bill (roughly double the usual, which has never been too cheap anyway). I started paying attention, and noticed that the heat pump was pretty much running all the time, just to keep everything at the right temperature.
After a couple of weeks, it went on a downward slope. I would have the thermostat at 74, but noticed that the temperature never went above 71 or 72, and it was still running all the time.
I called out the company that originally installed it, and after a lot of "I'm not sure" and "everything seems OK here," they finally guesstimated that the problem is what they called a "UV Valve." The tech said that all of the voltages were right, and everything was kicking on correctly, so this was literally the only thing left that it could be. He called the home office, and they sent out another guy a few days later to confirm (I wasn't here when he came to confirm, but he left me a voicemail).
Here's the problem: the estimate to replace this UV Valve was a whopping $950! The original tech said it would probably be $600, but the tech that came to confirm when I wasn't here was the one that gave the higher quote. This makes me worry that (a) they saw my nice house and cool car in the garage, or (b) they found out what business I own, and think that I have money to pay extra (which I don't have, thanks to the nice house and cool car in the garage!)
I don't want to go in to too much detail, but I also had to have a minor repair done to the heat pump after I bought the house that makes me question the quality of the original installers work. It seemed as if they installed something that they knew would fail, possibly with the intention of getting paid to come and fix it at a later date. I can explain more if necessary.
So here are my questions:
1. Based on the symptoms I posted, does the diagnosis of a faulty UV Valve seem reasonable?
2. If so, would an estimate of $950 seems fair to replace that valve?
I hate to say "please reply urgently," but the temperature here is going to be close to 95 by the weekend, so I have to decide pretty quickly whether to pay someone else a $100 "diagnostic fee," or to just trust this one. It turns out that every HVAC guy in the county charges a minimum $100 fee, just to come and look at the darn thing!
TIA,
Jason
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After reading further, the guy MUST have meant "reversing valve." I can't find anything on a UV valve except for in reference to gas heat, and a sticking reversing valve seems to have similar symptoms.
- J
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The mechanical principals behind a heat pump can't be that complex. http://en.wikipedia.org/wiki/Heat_pump I would check the fluid level. Then I would look around for a similar valve from a HVAC place and swap it.
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Replacing a reversing valve is a BIG job. First, they are soldered into the "outside" unit. When you open up the system you will expose the compressor oil to contamination from moisture in the air. It will require a longer than average "pump down" to restore the system. The existing R-22 (or whatever) will have to be "recovered" and not just dumped into the atmosphere.
The OP definitely needs to get a second opinion but this is definitely not a DIY project. Considering the age, it might make sense to replace the outside unit. His best bet is a one man shop type of operation.
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On Wed, 09 May 2007 05:34:51 +0000, PaPaPeng wrote:

Only problem is that valve changes the path of the freon. So the freon in the outdoor unit would have to be recovered (hopefully there are hand valves that isolate it from the lines) the valve replaced, vacuum pulled and then recharged. Also I think there are two such valves unless they've redesigned them with only one more recent than the 25 years ago I worked on them
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Don't worry, John, there's no way I would try doing this one myself! When it comes to DIY, I have a rule: if it can blow up and kill me, don't mess with it! ;-)
Based on the symptoms I posted, does a faulty reversing valve seem like a reasonable diagnosis? I can save myself $100+ if I call the repair guys and just tell them that I need a quote on replacing this specific part, instead of having them come out to look at it themselves.
- Jason
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On Thu, 10 May 2007 03:02:15 -0700, Jason wrote:

It's reasonable but without setting gauges, volt meter, ammeter on it I would hate to be responsible for you spending money to replace that valve only to find something else was bad.
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First let me preface my comments by saying that you may not want to take your air conditioning advice from a guy who writes software for a living (although I do have a degree in electrical engineering).
I assume that the checking up to this point has included proper freon levels.
20 years ago, had a problem with a Goettl (big brand here in AZ) heat pump on my roof. As others have said, in a heat pump, there is a reversing valve that basically reverses the direction of flow of the freon, so in winter you're removing heat from the outdoors and bringing it inside.
My problem was that when we got to winter and wanted to heat the house, we turned the thermostat to Heat, set the temperature, and things just got colder - the heat pump was stuck in cooling mode, so it was never going to reach the set temperature. Sounds kinda like your symptoms.
In my Goettl, the reversing valve was actuated by the house line voltage. Since thermostats do not switch line voltage directly (they operate on 24 VAC sent down to the thermostat from a transformer in the unit), there is a relay in the unit that is supposed to switch the reversing valve when you change the thermostat from cool to heat. In my case, the relay that controlled the reversing valve was sticking, not switching line voltage to the reversing valve. A good whack with the butt end of a screwdriver was enough to unstick the relay. Replaced the relay anyway on the theory that it would probably stick again. Cost - a couple hours of my time and about $20 for the relay.
My point is that it may not be something that has to touch the freon loop, where things start to get expensive. A simple check with an AC voltmeter will tell whether line voltage is getting to the reversing valve or not. Now if you have voltage to the reversing valve and it still is not working, then the reversing valve may be bad and you're going to end up opening up the freon loop to replace it - that is work that is definitely best left to a pro. Like others have said, the EPA wants you to recover the old freon instead of venting it to the atmosphere, then you gotta pump the system down before putting in new freon. And freon is pretty pricey these days, I think AC guys in Phoenix are charging around $100 a pound, I remember when you could walk into Pep Boys and buy a 1 pound can of freon for your car for about $5. But, if you know what you're doing around electricity, can read a simple schematic, and have access to an AC voltmeter, a little detective work can point you in the right direction.
Hope this helps, Jerry
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