3 Possible Explanations for Intermittent Air Conditioning Shutdowns

by Fransic verso
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Explanations for Intermittent

Air conditioners are susceptible to wear-and-tear and operate less efficiently over time. In fact, in our 40 years of experience as an air conditioning company in West Berlin, NJ we have seen many times a confirmation of the rule-of-thumb that an AC unit loses on average 0.5 point of its nominal SEER each year.

If you purchased a brand-new air conditioning system 5 years ago with a SEER of 16, the actual efficiency rating of the unit is probably right around 13.5 today.

But even if an AC loses efficiency, it should still operate and blow cold or warm air. If it struggles to cool you of when you need it, or sometimes works well and sometimes does not, or worse, if turns on and off unexpectedly, you can suspect these 3 causes: thermostat malfunctions, airflow issues, and electrical failures.

Most air conditioning companies will check these issues if you call for an emergency repair. But they may also overlook them because of their intermittent nature. These 3 issues deserve to be checked thoroughly.

Let’s dive into them.

Thermostat Malfunctions

The thermostat regulates the operation of your air conditioning system based on the temperature in your home and your desired temperature setting. Faulty thermostats can misread room temperatures or fail to communicate correctly with the HVAC system. This will be enough to cause your compressor to cycle continuously (start-run-stop-star-run-stop).

Airflow Issues

Your AC can’t work properly if its airflow is constrained. The typical cause of low airflow is clogged filters. Clogged air filters cause a system to work harder to circulate air. This leads to overheating in the compressor and blower motor, accelerating wear-and-tear, and potentially causing system shutdowns.

Electrical and Control Failures

Electrical components are susceptible to damage from power surges, corrosion, and regular wear. Faulty wiring disrupts power supply, with both intermittent and complete system shutdowns. Control board issues cause improper functioning of various system components. Corroded contacts in relays and switches impede electrical flow.

These types of causes can be fixed either by yourself (filters) or by a professional air conditioning company. If chancing your air filters does not do anything to improve the performance of your system, it’s probably time to call an HVAC contractor before the problem degenerates into more costly repairs.

Here is how our NATE-certified technicians address all these issues, one by one.

Remedying Thermostat Malfunctions

  • Diagnostic Assessment: Our technician starts by assessing the functionality of the thermostat does it display the correct temperature? Does the electronics respond to input changes?
  • Inspecting Wiring Connections: Then our technician checks the wiring connections between the thermostat and the HVAC system, looking for any loose or corroded connections likely to disrupt the communication between the two components.
  • Testing Thermostat Calibration: Once the wiring is inspected, we will verify the accuracy of the thermostat with a thermometer. If we find discrepancies, we recalibrate the thermostat. If the unit is faulty, then we’ll recommend its replacement.
  • Replacing Batteries: Some thermostats use batteries. Believe it or not, this is a very simple cause of malfunction that is often totally overlooked. Dead batteries must be replaced.
  • Thermostat Location: Our technician checks if the thermostat is located in a spot where false readings are possible: in direct sunlight, near heat sources, or in drafty areas. It sometimes is necessary to relocate the thermostat in a temperature-neutral area of your home.

Airflow Issues

  • Inspecting Air Filters: Though it is a very obvious thing to check, many homeowners just don’t really think of their filters as being dirty.

    Yet, filters do collect dust particles and over time, excessive dirt buildup restricts airflow at the return vents. Dirty filters must be replaced.

    The replacement frequency varies based on the geographic area and the level of dust in the home. In Arizona for instance, home tend to gather desert dust very quickly, and air filters must be changed once a month.
  • Checking Air Ducts and Vents: As a general precaution, we inspect the air ducts and vents for blockages, leaks, or disconnections capable of impeding airflows.

    Sometimes the solution is as simple as showing the homeowner that a piece of furniture is placed right in front of a return vent. That furniture must be moved to let the AC “breathe” normally.
  • Evaluating Blower Motor and Fan: Our technician will of course check the blower motor and the fan to make sure they operate properly. When fan belts are worn out, for instance, a fan will not rotate at the right speed, sometimes not at all, and cause airflow issues.

    Sometimes, the fan has been hit and its blades have become misaligned, which will limit its pulling capacity.
  • Assessing Evaporator and Condenser Coils: Lastly, our technician will ensure that both coils are clean and undamaged. Dirty or frozen coils will restrict airflow and prevent the compressor to operate normally.

Electrical and Control Failures

As mentioned above, electrical connections can be loose or corroded, and in this case, an AC system will start and stop for no apparent reason. Corroded terminals can prevent the passage of electricity.

  • Inspecting Electrical Connections: Our technician examines all electrical connections between the compressor and the rest of your HVAC system. He or she must tighten any loose connections and replace corroded or damaged wires.
  • Testing Capacitors and Relays: Using a multi-meter, our technician tests the capacitors and relays of the compressor. They need to be replaced if the measurements values are outside of factory specifications.
  • Evaluating the Control Board: In a split system, the control board is typically located within the air handler or the furnace component usually found in a basement, attic, utility closet, or garage. It is housed in a metal box often situated near the blower motor.

    It’s designed to be accessible for maintenance and repair but is usually not in an area that’s easily reachable without removing a panel or door.

    Our technician will measure the inputs and outputs of the control board to find out if it is defective. Electronics deteriorates over time, solder becomes loose and faulty connections can occur.

    This is often the case in home where the air handler is under the roof. There, temperatures can reach upwards of 100°F, and vary brutally overnight. This is enough to create this type of issues. Our technician usually replaces a faulty control board.
  • Testing Safety Switches and Controls: Some safety switches and control like the pressure switch and overload protector can trip falsely, causing the compressor to shut down. They have to be checked.

Apart from the cleanliness of your air filters and the space around your return vents, all of these issues have to be addressed by a professional air conditioning company. If you unit is under warranty, it would be foolish to risk voiding it because you like to DIY.

This article is not meant as a step-by-step procedure. It is just a view of how we test three possible causes of intermittent malfunction for an air conditioner.

About the author

Filan & Conner is a 40-year old air conditioning company located in West Berlin, NJ. The company covers all the spectrum of the air conditioning business: repair, maintenance, and installation/replacement.

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