Towards the end of the service life of any mechanical system, repairs are only temporary in nature.
I wrote before about the Weibull curve and how every piece of equipment has a design service life. Some people find this appalling, thinking that equipment should last forever and that but-for "planned obsolescence" it would. But the reality is, everything breaks down over time, and by break down I mean revert to its original components. Steel turns back into iron oxide from which it came. Even plastics, once touted as the miracle material of the future, will become brittle, crack and turn into powder and dust over time.
We learned the latter with our microwave - now 14 years old and near the end of its design life. I was chagrined to pull the handle on the door and have it come off in my hand. Turns out the handle is mounted only to the ornamental trim plate on the front of the door. I found a video on YouTube on how to remove this piece, and using Marty's Matchbox Makeover technique of superglue and baking soda, was able to patch the plastic together. I put painter's tape on the outside of the door panel, so the superglue would not seep through. The crack has largely disappeared and the handle is now firmly in place. It works for now, but eventually - and soon - we will have to buy a new microwave, along with a new stove, dishwasher, refrigerator, and so on and so forth. If you have a microwave, be gentle to the handle - judging by the number of YouTube videos on this topic, these things breaking is quite common.
In addition to parts wanting to revert to their component chemicals, there are other forms of failure, which, over time, are inevitable. Mechanical parts will wear against each other. Electrical components will degrade. Eventually everything falls apart. As an engineer, you can try to make things last forever, but they will end up costing so much money that no one can afford them. A better approach is to make something affordable and design for a certain design life. For components that won't last that design life, you design them to be accessible and readily replaced.
For example, back in the day, a car was expected to last less than 100,000 miles. And during that time, it might need its spark plugs changed several times, the points and condenser changed almost annually, the oil change several times a year, the tires changed every 20 to 30,000 miles and so on and so forth. Going back even further in time, many cars would have a valve job done every 30,000 to 40,000 miles if not more often. Cars of that era were designed to be worked on constantly, which is why cars had a hood over the engine that could be easily opened.
I said before jokingly, but it probably will be true someday, that in the near future you'll buy a car and there won't be a hood release. Rather, the hood will be bolted in place with a sticker saying "no user serviceable parts inside!" And you won't really need to open the hood for any reason because the car engine will last for the life of the car. And if it does need service, there's nothing you could do, as the owner, to work on it.
Indeed, today, things that were replaced periodically now last the life of the car. Spark plugs can last a hundred thousand miles or more. Ignition systems are solid-state and last equally as long. Even car batteries, which once had to be replaced every two years, sometimes last as long as a decade.
And although we have made progress, cars don't last forever. In fact, they still are designed for design life of about a hundred fifty thousand miles or 15 years. If you get service life beyond that it's a bonus. But don't count on it, despite how many advertising campaigns Subaru runs.
As I noted in the Weibull Curve posting, there are two modes of failure for equipment systems. Early on in the life of an apparatus, there will be failures (so-called "infant mortality) due to errors in construction or faults in component parts. This is why we have warranties. Then, during the middle portion of the life of the apparatus, it'll be at its most reliable, as the teething pains have been sorted out and nothing is yet to wear out. That's why extended warranties are often no bargain. Then, toward the end of the life of the system, parts will start to fail, one after another, until the cost of repair exceeds the cost of a new system or item.
It's at this end of life part where people end up throwing money at equipment and end up unhappy. It first, it seems appealing - you can fix something for not a lot of money compared to the cost of replacement. And sometimes, it is worthwhile to do some repairs, but don't fall into the trap of paying money for repair after repair, when the end is near.
(Oddly enough, humans are the same way. More than half the cost of our health care system is spent on end-of-life care, spending hundreds of thousands of dollars prolonging life by mere days or weeks, often at great inconvenience and discomfort to the person involved. Odd how we use the terms "infant mortality" and "end-of-life" in both Engineering and Medicine!).
It is easy to believe that anything can be fixed, and indeed, anything can be fixed, if you throw enough money at it. People "restore" old cars, and they seem like new, but you notice those folks rarely drive them - or rarely use them as daily drivers. While a lot of things may have been rebuilt or repaired, a lot of other things are ready to fail - and parts might not be readily available. The antique car may still "work" but it is as fragile as glass at this point. It is more of a talisman of a car than a car. It is a 4,000 lb paperweight.
The other pitfall many folks fall victim to, is the "fix it for good!" mentality. A part fails on a ten-year-old 100,000-mile car. They go to the parts store or go online and find the replacement OEM part for cheap. But someone online (a shill) or a salesman at the store, offers to sell them an enhanced part for twice as much money. "This super-duper coil is made of unobtainium! You'll never have to replace it again!" they chirp. But the reality is, the cheap OEM part lasted 100,000 miles, and its replacement will last as long, or in other words, longer than the remaining life of the car. Throwing parts at an near-end-of-life car is dumb. Throwing fancy parts at such a car even dumber.
What got me started on this was that we had the HVAC guy come by to check out our system as part of the service contract. As I suspected, the system was low on charge, as it wasn't cooling as well as it used to. He added three pounds of refrigerant and the house is like a meat locker now. He pulled the access panel off the air handler (the inside part) and using an electronic leak detector, spotted a leak in the "A" coil (evaporator coil). It was the beginning of the end for this HVAC system.
A new "A" coil, on eBay is over $1200, and that doesn't include installation. From the service tech's point of view, it is a lot easier to install a whole new air handler, rather than take one apart and put the new coil in. Replacing the coil myself is a little beyond my skill and tool capability, although I now have a vacuum pump and manifold gauge set after I installed the split system in the garage.
Not only that, when you add up the cost of the coil and the labor, it is darn close to the cost of replacing the entire air handler, if in fact, a lot cheaper. Now, if you have the time, tools, and skills, it is possible to do many repairs yourself. For example, when I was at Carrier, one of the techs told me how he replaced the heat exchanger in his furnace, after it had cracked. In a gas furnace, there is a heat exchanger - basically a big metal box - that the flames shoot into. The exhaust gases go up the chimney while the air on the other side goes into your house. If the exchanger rusts out or cracks, the exhaust gases can go into your house and kill you as you sleep. Sort of like old VW Beetle heaters - which used exhaust heat to heat the car.
Anyway, he found a replacement heat exchanger and tore down the furnace and installed it himself. Since it is the heart of the furnace, he basically had to take apart the entire thing. Not a problem for a guy who is an HVAC tech with all the right tools. A little overkill for us ordinary folks. Compounding this problem is that by the time the heat exchanger wears out, it is over a decade old and odds are, no one carries the part anymore. My friend lucked out in finding one for cheap in the back room of a local HVAC distributor, who just wanted to be rid of it (because no one replaces these!).
The other problem is the rest of the furnace is 10-15 years old, and likely will fail soon. That blower fan has been running for over a decade now, how much longer will it last? In our home in Virginia, we had a Chrysler "Air Temp" furnace that the previous owner had added a heat pump to. The furnace was streamlined with a hammertone paint finish - no doubt designed by Raymond Loewy. It may have been original to the house, or replaced long, long ago. Anyway, after living there a few years, the blower fan stopped working. I took off the access panel and removed the blower (turning off the power first!) and found it filled with dust (dead human skin), cat hair, and whatnot. I cleaned it off and found it was hard to turn. But being "old school" the motor had oil caps on each end, and I dripped some 3-in-1 oil into them and rotated the fan until it turned freely.
I had some experience with this, with the enormous rooftop unit at my office, which had a similar problem. I also replaced the run-start capacitor, which gives an AC motor a little jolt to get it started (most AC motors will not start turning under their own power, when turned on, without this capacitor). I put the blower motor back in and voila, it worked. I also vacuumed a pile of rust out of the heat exchanger and realized this was an old, old furnace near the end of its design life. I went out and bought a carbon monoxide detector.
I was able to nurse that furnace along for a few more years, but I realized I was playing with fire (quite literally) in that if the heat exchanger cracked, we would all die of CO poisoning. Why are my fingertips turning blue? I finally broke down and bought a new furnace, which cost the princely sum of $1800 back then. Fortunately, the heat pump never needed much other than occasional top-off in charge.
For my rental properties, I didn't mess around - I put in a new furnace in the duplex once I realized the old one had a rusty heat exchanger. Wrongful death suits get expensive. And we eventually replaced the rooftop unit at the office, too. I had stopped using the furnace feature for some time (using the heat pump instead) as the heat exchanger was quite old.
A reader writes that his A/C unit stopped working and he went out to look at the condenser unit and realized the fan blades had rusted off. He spent $350 buying a new motor and fan, and put the thing back together. Probably worthwhile to fix, at that price, but I advised him to start saving his pennies for a new system, as eventually something else would wear out. If the fan is rusting off its mountings, one can only wonder how the coil is holding up.
Replacing parts piecemeal costs more than replacing entire systems. If you have separate service calls for the condenser fan, condenser coil, compressor, the A-coil, the blower motor, etc, it could easily add up to well over ten thousand dollars - and the resulting system, being worked on so much, would be less reliable. You could install a whole new system for less than half the amount, in many cases - the labor is far less and the parts cost, overall, is far less. And the result would be a more reliable system (assuming you get past the warranty/teething pain period).
Sadly, a lot of people don't get this. I wrote before how the guy I bought my Fiat from got frustrated by repairs. Trying to be "cheap" he paid only for what broke each time he took it in. So the left front lower ball joint was bad - he replaced that. The next year it was the right front upper ball joint. And so on and so forth. He ended up paying two or three times as much as it would have cost to just replace all the ball joints at once. And it goes without saying that people with no mechanical skills have no business owning a 20-year old Fiat.
The air conditioner is working for now. I am going to get quotes for replacement, and probably will replace the entire system. Replacing only piecemeal parts (the air handler, for example) might be short-sighted, as eventually the compressor will fail and the condenser coil will leak. Also, if I had to sell the house, it would be easier to sell with a whole new system, instead of some piecemeal replacement. And I likely would replace the refrigeration lines at the same time, even though the tech claims they are "just fine the way they are."
But depending on how slow the leak is, I may not replace it right away. And I may look into my idea of replacing the system with split systems, although I suspect that will be more costly, even if I install these myself. In addition, it might make the house seem quirky. There are some folks here on the island, who, as they got older, ran out of money. When the HVAC system crapped out, they could not afford to replace it, so they put window units in a number of rooms (which are only a few hundred dollars apiece). While this worked fine for them (and since they left the island feet-first, and didn't give a rat's ass about resale value) it doesn't help the resale price of your house.
Of course, it may be possible to just keep putting refrigerant into this system, and then getting naming rights for part of the ozone hole above the Antarctic. A friend of mine is facing a similar problem, and since he lives "paycheck to paycheck" he cannot afford a new system. "I can put a lot of refrigerant into it, $300 at a time" he says (and that is what the techs are charging these days, with labor), "until I can afford to pay for a whole new system!" It is like the lady we met who paid $6 a day for the parking permit, for over a week, because she could not "afford" a $45 yearly pass.
R-22 refrigerant, which our current system uses, is going to be phased out. But you can still buy a 10-pound can of it on eBay for under $200. I suppose I could buy some, and with my manifold gauge, keep topping off this system for another year or so. But it is just delaying the inevitable.
Owning a house is so much fun! Now you can see why I like the idea of living in a Park Model. When the A/C craps out, you just go to WalMart and buy a new window unit for a few hundred bucks.