What’s the BIG Problem with my AC?

Every season there will be a fair number of people with small problems in their air conditioners. They’ll experience leaks, failed belts, and maybe a few minor electrical issues. These are all little wear and tear things that your contractor can fix for a few hundred dollars. When an air conditioner gets older however, things start getting a little more expensive. There can be some big things starting to fail.


Dead Compressor

The compressor is that big, typically black, cylinder or spherical object in your air conditioner. In many ways it is the heart of the system. The compressor will receive refrigerant and through one of many ways, squeeze it down. This compression is what lets us remove heat from the air elsewhere in the system. When the compressor fails or begins to fail, you might experience warm air blowing from the air conditioner instead of cold air, regardless of temperature setting. The system may have difficulties starting up, draw excessive power, burn through fuses, or trip its breaker.

When the compressor fails, there’s really only two areas things can go wrong: the motor or the compressor assembly. If the motor starts to go, it’ll perform poorly and draw more power to start and run. Eventually the motor will just get hot and stop cranking the compressor assembly altogether. At that point, it’ll probably blow a fuse and start melting internal components. On the other hand, there’s also a mechanical compressor that is not immune to break downs. The failure points vary from design to design, but typically there are internal valves and seals that can go bad. When these start to fail there will be a loss of compression, just like a car with a failing head gasket. When there is no compression, the whole system is pretty much dead in the spot.

The repair for this is to replace the compressor, but that can be expensive. Even small compressors like those used in Mini-fridges and window air conditioners can start around the $200 mark. For a central air system, expect to pay much more. Your contractor then needs to remove some piping and wiring to get the old one out, re-do any fittings he removed, recharge the system with refrigerant, and by now you could be looking at over $1000 for repairs in some systems.


Failed Coils

There are two coils in the air conditioner as well, an evaporator and a condenser coil. These coils are where heat is radiated outside and where inside air is cooled down. When these go bad, the coolant leaks out quite quickly and you’ll get only hot air. The failure can be due to aging, parts just rusting up and leaking and environmental damage from the system icing over. If you hear a hissing sound near your indoor air handler, fridge, or window/standing air conditioner, you probably have a refrigerant leak, possibly from one of these coils. Open the windows to vent the air and evacuate the area immediately. Not all refrigerants are safe to expose yourself to.

When these coils go bad, things get to be expensive fast. In most cases, it is advised to replace both coils at the same time. The two coils must be a matching-pair and if one coil failed there’s certainly a good chance the other can’t be far behind. If you have a 5-ton evaporator coil, most manufacturers prescribe a 5-ton condenser coil to work with it. The coils come in all sizes and price ranges, but like compressors, they’re not exactly cheap.

Like the compressor repair, replacing coils involves removing and replacing fittings before attaching the new parts and recharging the system. This work can go on both inside and outside the building to get at both coils. For large commercial facilities, it may be necessary to rent a crane to get the coils into position. Bigger systems means bigger, hundreds-of-pounds coils.


Thermal Expansion Valve

Our last big-bill item is the valve that regulates the evaporator coil. This regulating should improve the coil’s efficiency and ultimately save power in the long-run. When this valve begins to fail, there are a wide array of potential symptoms. The system can perform poorly, stop altogether, leak refrigerant, or in some cases appear unchanged if the valve manages to seize in the open position (except for the higher utility bills).

The valve itself can actually be a pretty cheap part. We’ve seen some of these valves in the $100 range and above. This can however be a more labor intensive repair, depending on the actual design of the system. The expansion valve is usually near one of the coils, if not fitted near directly to the coil. In the tight confines of an air conditioner, it may be necessary to remove the coil altogether in the process of getting the valve off. If the coil is sufficiently worn itself, it could end up broken in the repair process. Once everything’s apart, the new valve can be soldered on, along with the coil and anything else that came off.


The Key to Expensive Repairs

As a rule of thumb, most components on the air conditioner are cheap enough to replace. The major exception however, is anything with a pipe going into it. You can replace most electrical parts by cutting the power, removing a few wires and a few screws, and you’re back in business. Anything with plumbing however, is going to be more complicated. Once the refrigerant connections are involved, the system must be drained, chances are other parts must come off, and it’s going to be more expensive in labor than the repair may be worth.

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