How to Troubleshoot a Residential Split HVAC System
It never seems to fail that, in the midst of a heat wave, something goes wrong with your air conditioner. Fixing an air conditioner is really best left to trained professionals, but troubleshooting to find the problem can be done before you make that call. Sometimes the fix can be as simple as a tripped breaker or a clogged drain hose. Other times you will have to call a professional, but you can save time and your money by knowing where the problem is located before he arrives. Does this Spark an idea?
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Instructions
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Locate your electrical service panel. Open the cover and look at the rows of breakers. A tripped circuit breaker can be indicated by its appearance: it will ether have a little orange flag visible or it will look misaligned with the uniformity of the others. If the breaker looks like it is in the halfway position between on and off, it is "tripped." To reset the breaker, push it to the off position and to the on position again. If it trips off when the AC unit tries to start again, the trouble could be a shorted compressor or fan motor. Call a professional in either case. Do not open the condenser electronics compartment unless you first shut off the power.
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Look inside the cabinet to see if the capacitor is grounding to the cabinet or if a wire has fallen off or burned into two pieces and is grounding out. Use electrical tape around the wire connections to isolate the terminals from the cabinet. The wire that may have been burned in two will need to be stripped back and reconnected.
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Check that the indoor fan is working. Turn the thermostat fan switch to the "fan on" position. If the fan will run indoors, the fan motor is not at fault. Turn the fan switch to the auto position and move the mode switch to the cool position and set the AC down to its coldest position. If the indoor fan does not come on, the fan relay is not working or it may be hat the circuit board that controls the fan has failed or a bad run capacitor is in the fan circuit. Either way, call a professional, who will order the parts to be replaced.
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Go into your attic if the indoor part of your AC is there. Look at the secondary safety pan to see if it is full of water. Many units have a float switch to shut off the unit to keep it from ruining your ceiling with the water it produces. If the pan is full of water, then both the primary and the secondary drains are blocked by the algae that will grow in such pipes. Use a shop vac to remove the clog from the pipe if the plumbing has been set up with a proper service port. To clear the water from the secondary pan, locate the exposed pipe outside, usually up high, beneath the eaves. Apply suction outside and you won't have to carry the heavy water down a ladder.
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Check the low voltage wires that connect the thermostat to the furnace and the furnace to the outside condenser. Mice have been known to chew these, causing short circuits. If you notice a badly chewed wire, use electrical tape to isolate these wires from one another.
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With the thermostat set on cool and the temperature selection set on the coldest position, check that both the indoor fan and the outside condenser come on. If both of them do, use your thermometer and read the outdoor air temperature, then read the air temperature being blown out the top of the condenser. The temperature should be 10 to 20 degrees warmer than the first air temperature that you just read. Another check of refrigerant charge is to feel the temperature of the suction line. There are two copper pipes that come out of the condenser: a small liquid line and the larger gas suction line. With the condenser running, the suction pipe should feel like a cold can of soda, but not frozen. If it doesn't then refrigerant may need to be added. Call a professional to do this, because there are special tools required and they are not cheap. There are also different types of refrigerant, so check to see which refrigerant your system uses. R-22 or R-410A are in most residential air conditioning systems.
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Check your filters. They may be plugged up with so much dust as to restrict airflow. If so, clean them thoroughly or replace them.
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Tips & Warnings
Give a good description of the problem if you still need to call a professional.
Always make sure the electricity is off before you go near the unit. Never troubleshoot while a fan is on.
