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Central AC Repair

How we Repair Central AC System Icing or Freezing Problems.

Central air conditioning icing over or freezing can be caused by low charge, a problem with refrigerant flow or air flow, a failed thermostat, a problem with controls, or some combination of these different issues.

Proper diagnosis procedure will be to isolate the specific problem. Starting with the thermostat, make sure it is working and that the electrical contacts open and the compressor stops when the thermostat temperature setting is met. You will need to set the temperature setting at a temperature higher than the current indoor temperature to verify this. The idea here is to make sure the compressor contactor is not powered when the thermostat is not calling for cool. A failed thermostat, loose wire or a short circuit could keep the contactor powered and cause the compressor to keep running when the evaporator fan is off. This is one common issue that can cause central air conditioning systems to experience icing problems.

If the thermostat test shows that it is working properly, next we will check for air flow problems by inspecting the evaporator and making sure it is clean. If it has accumulated dirt, it must be cleaned. Also, at this time we need to check the air filters and either clean or replace them. The blower fan must be checked to see if it is running at the correct speed and blowing in the proper direction, and see if it has accumulated dirt and make sure it is cleaned if necessary. Also, make sure the duct work has not failed and is properly delivering air flow.

If it has been determined that air flow is not a problem, its time to connect gauges and begin to check out the refrigeration processes of the air conditioner. For this procedure you will use the manufacturer’s specifications which should be available through the manufacturer’s website. If not, follow the ASHREA recommended procedures and stay in compliance with AHRI guidelines.

Once you've verified that you have good air flow through the air handler, if your central air conditioning icing problem continues, you'll have to hook up gauges and check your pressures. At this point, as you check pressures, note that a suction pressure that's equivalent to 32F or lower is the most likely cause of central air conditioning icing problems. When you see a low evaporating pressure and temperature, and if you have high superheat and low sub cooling, you most likely have a low refrigerant charge.

If you find that there is low suction pressure and nearly normal discharge pressure, with high superheat and high sub cooling, you will probably find that there is a restriction of malfunction in the expansion valve or drier.

At this point, if air flow, pressures, temperatures look normal, it’s time to look at the controls for crossed or loose wires and test the evaporator relay controls. If these contacts are opening and turning off the evaporator fan while the compressor is running, the coil will ice up, and this is very serious- it can cause the compressor to fail. Make sure the compressor contactors have not arced themselves to a closed position.  If this has occurred, the compressor will run continuously without regard to the thermostat setting, and can cause the freezing over.

Instant Air Repair subscribes to the proper procedures. Instant Air Repair operates across the areas of St. Petersburg and Pinellas County including, Belleair, North Redington Beach, Belleair Beach, Oldsmar, Belleair Bluffs, Pinellas Park, Belleair Shore, Redington Beach, Clearwater, Redington Shores, Dunedin, Safety Harbor, Gulfport, St. Pete Beach, Indian Rocks Beach, St. Petersburg, Indian Shores, Seminole, Kenneth City, South Pasadena, Largo, Tarpon Springs, Madeira Beach, Treasure Island.