Detecting a Faulty AC Relay Switch: 5 Signs to Watch For

One of the most common air conditioning repairs technicians make in the summer months is replacing a faulty AC relay switch. Like many components in electronic devices, parts inside air conditioners can wear out and malfunction over time. Unfortunately, many of these malfunctions occur on the warmest summer days, leaving you and your family feeling overheated and uncomfortable. 

Staying alert to the signs of a failing relay switch helps ensure you schedule professional repairs before a broken part stops the air conditioning from working altogether. Sometimes, even a seemingly minor noise or slight change can signal major trouble brewing. However, ignoring them can lead to expensive and inconvenient repairs.

Premier Systems, the leading AC repair experts in Bozeman, are ready to help local homeowners keep their air conditioners running all season. Here, we highlight some of the most common signs of a failing relay switch so you know when to call us for help. If you notice any of the following issues, call us at (406) 629-1583 to schedule repairs. 

What Is a Relay Switch in an Air Conditioner?

Every electrical system uses a series of switches to help control the electric current. When a switch works correctly, electric current flows between two terminals without interruption. A faulty switch prevents the current from flowing; the switch may be open, but there's no current or power between the terminals.

In an air conditioner, the relay switches send power to the compressor, which is the heart of the system. Without the compressor, the air conditioner would be unable to remove heat from the air inside your home and replace it with cooled air. 

The compressor turns refrigerant inside the coils from a cool, low-pressure liquid into a hot, high-pressure gas. This high-temperature gas supports evaporation, which produces the cold air that blows from the air conditioning vents. If the compressor fails for any reason, the air conditioner cannot produce cold air.

The Most Common Signs of a Faulty Relay Switch 

In many cases, it's easy to spot a problem with the air conditioner's relay switch. To help you recognize trouble in your home air conditioning system, here are some of the symptoms and signs of a faulty AC relay switch.

1. Weak Cooling 

If your air conditioner isn't producing very much cold air, even on the highest setting, the compressor may not be getting enough electrical current to compress the refrigerant. A failing switch doesn't transmit adequate load current from the power source, preventing the compressor from creating the liquid refrigerant that cools the air.  Without adequate pressure, the refrigerant will remain a gas and won't flow into the evaporator coils and remove heat from the air.

Eventually, a broken relay switch will prevent the compressor from working at all, resulting in only warm air flowing from the vents. 

2. Intermittent Cooling 

Another sign of a failing relay switch is intermittent or inconsistent cooling. When the compressor does not receive adequate power, it may work sometimes and not others. Worn contact points inside the part lose their ability to consistently make and break connections, which can result in unreliable cooling. 

In addition to age-related wear and tear, dirt and contamination accumulating on the contact points inside the switch can result in contact resistance. This eventually contributes to switch failure and causes intermittent function issues with the air conditioner. If you're holding your breath and hoping that the air conditioner turns on when you need it, it's likely a relay issue. 

3. Odors

Sometimes, a faulty switch can cause a smoke or burning smell. A bad relay connection can produce a great deal of heat, and this excess heat can cause the plastic coating on the internal wiring to melt and produce an unpleasant odor. In extreme cases, the excessive heat can even cause a fire inside the air conditioner's outdoor unit. 

4. Noise

One surefire sign that the relay switch is faulty is that the compressor does not turn on. Typically, you will hear the compressor turn on when the air conditioner turns on. This is typically a series of clicks as the clutch turns on and engages, followed by the low hum of the blower motor. 

If you turn on the air conditioning and do not hear any clicking sounds, the compressor most likely is not receiving any power, so it cannot kick on. If you hear a rattling noise or it seems like the air conditioner is having difficulty starting up, it often means the switch is starting to fail. 

5. Higher than Usual Electric Bills 

Because the air conditioner has to work much harder to start up and produce cold air when the relay switch is not working correctly, it uses significantly more power than usual. This can cause a noticeable increase in your power bills. Keep an eye on your bills to catch problems before they drive up costs and ensure energy-efficient cooling.

Diagnosing a Faulty Switch 

HVAC technicians can check for faulty relay switches using a multimeter or voltmeter. A multimeter can determine whether the electric current flows consistently between two terminals. A voltmeter checks the voltage in each terminal, ensuring both sides of the relay have the same voltage and neither side has low power or exceeds the voltage rating. 

If tests show that the current isn't consistent or the voltage isn't correct, replacing the relay switch may solve the problem. If it doesn't, the issue is elsewhere in the air conditioner. In either case, for safety reasons, repairing and replacing the electrical components of an air conditioner is a job best left to the professionals.

Air Conditioning Repair Services from Premier Systems 

Premier Systems understands that staying cool during the Montana summer is a priority. We are here with a full array of air conditioning installation, repair, and maintenance services to help you do just that. As the leading heating and cooling provider in the area, our licensed and educated technicians have the experience you can trust to preserve indoor comfort all year round. 

When you call us for help getting your air conditioner working again, we'll perform a full inspection and evaluation. Once we determine the issue, we review information with you about the repair options and costs and help you find a solution that keeps you cool and fits within your budget. We carry most parts and supplies in our fully-stocked service vehicles, so most customers do not need to wait for parts to come in before they have a working air conditioner. 

If we determine that replacing your air conditioner is a better option, we will walk you through the process and help you choose a reliable and energy-efficient option and provide professional AC installation. Ask about Premier Club membership, our money-saving maintenance program, to keep your home's HVAC system in top working condition. Club members enjoy annual HVAC maintenance service, which helps ensure your system operates at peak efficiency every season. 

Make an Appointment for Air Conditioning Repair Today 

Don't let a failing relay cause an air conditioning malfunction that leaves your family uncomfortable or puts the system in danger of total failure. If your home's air conditioning is not working as expected, and you suspect that the problem is a faulty AC relay switch, contact Premier Systems for  prompt and efficient repairs. Our technicians can quickly identify the source of the problem and make repairs to restore indoor comfort.

Make an appointment by calling our Bozeman, MT, office at (406) 629-1583.