Summer is on it's way, and with it comes the seasonal worry that something unfortunate may happen to the most important piece of equipment in our homes, second only to the indoor plumbing. I'm talking about the Air Conditioning unit, be it the massive central unit cooling the whole house, or the window A/C cooling the sleeping quarters. Nothing contributes more to a happy, healthy night's rest than the degree of comfort afforded by a properly tuned and set an air conditioner. When working properly, we don't give it much thought, but when the temps outside start climbing into the mid 90 degree range, the system can be pushed to its limit, and it is a good idea to prepare for the inevitable, awful, sweat-soaked quiet that results from a failed system.
Central air conditioning units are divided into two parts, the compressor/condenser, most commonly located outside the dwelling, and the air handler/evaporator, which can usually be found in the attic, garage or a closet inside the home. In this article, we'll discuss a few things that could go wrong with each, and a how to make simple repairs that may save you hundreds in repair bills. Keep in mind, this article is being written for the homeowner with basic knowledge of hand tools and their use, and a healthy respect for the power of electricity. If you have neither, please seek the help of a qualified air conditioner service to assist you before attempting this, or any other, home repair project.
The Compressor is the large, noisy cylindrical or square metal cage located outside the dwelling. It's job, in simple terms, is to compress an oil based refrigerant gas, until it reaches a liquid state. A valve then releases the hot liquid (remember from Science class, a liquid under pressure heats up) to the air handler inside the home through a copper line. Inside the air handler is a part called the evaporator that looks like a small radiator in your car. Another valve releases the hot liquid into the evaporator, (again Science class, compressed liquid sprayed at very high pressure gets wicked cold). Now, the fan inside the air handler has been running all this time, moving hot air from inside your home through the insulated box which houses the evaporator, where the now very cold liquid-turned-vapor if flowing through the radiator-like structure of the evaporator, causing the hot house air to become chilled. The fan continues to force the now cooler air back into the various rooms of the house via a system of ducts and registers, to eventually be sucked back upstairs by the return air duct, to begin the air cycle all over again.
Remember that hot liquid oil back up in the evaporator? As it was sprayed into the evaporator and got chilled, it absorbed the heat energy from the hot air, and then it becomes a warm gas, which is then forced back outside via a different copper line to the condenser, where a large fan cools the gas by forcing it through the condenser, which again acts like your car radiator, further cooling the gas, before it goes back to the compressor to start the trip all over again.
Sounds simple, what could go wrong?
Well, a few things, and usually when a part of one system fails, it affects the whole system. Most commonly the problem is in a start capacitor, a small tin can looking thingy that takes household current, and amplifies it in order to give a starting boost to a large electrical motor, like the compressor outside, or the fan inside the air handler. If the compressor start capacitor is bad, you will hear a loud click coming from the compressor as it struggles to start, then a second later, a smaller sounding click when the motor in the compressor gives up trying to start. This will happen many times, and is not difficult to diagnose, or fix. Remember to respect the power of electricity when performing this repair.
Turn off the power to the unit!
It should be clearly marked in your home's circuit panel, most building codes also mandate a second breaker near the compressor itself. Remove the access panel, and locate the start capacitor. Using a rubber glove and an insulated handle screw driver, short-circuit the terminals on top of the capacitor. This is super important, as the capacitor stores up very high voltage, even after the unit has been turned off! Then, take a picture of the various wires connected to the top of the capacitor, so re-connecting the new one will be easier. Simply match the numbers on the capacitor to the new one, usually available at a better-stocked electrical supply company. Google one in your area that does retail sales.
The same thing can happen to the start capacitor in the blower motor, simply follow the same procedure as before, remembering to discharge the power stored inside the capacitor.
If you are getting warm air blowing out the vent, make sure the system is set to 'cool', and the fan set to 'auto'. Check outside to see where the condensate drain is located, and make sure it is not blocked. (Condensate is the moisture that is 'pulled' out of the warm house air when it passes over the evaporator, is forms as dew on the evaporator, then drips to a collection pan and down the condensate drain line to the outside). This would cause water to accumulate up there in the air handler, causing the safety switch to stop the flow of liquid through the system. The drain line usually becomes clogged with scum, and needs to be sucked out clean with a wet-vac, in order for the system to restart.
Corroded wires are a common problem within the compressor housing, especially in salty environs. This problem usually takes an air conditioner technician with the proper electrical meters to diagnose this problem.
Remember to keep the area around the compressor clear of accumulated leaves and debris, and your system should remain trouble free the whole summer!