Top 4 Signs of AC Contactor Failure

At Brookside Heating & Cooling, we know New Hampshire homeowners need powerful, reliable air conditioners. This includes a functional AC contactor.

As the bridge between your thermostat and the high-powered components of your air conditioner, a working AC contactor is necessary to ensure you experience the cooling you need this summer. When these contactors fail, your comfort can be compromised.

In this article, our HVAC experts highlight the critical role of an AC contactor, what happens when it is faulty, and simple instructions for testing it.

What is an AC Contactor?

When you set your thermostat to a lower temperature, a signal is sent to the contactor, allowing high-voltage power to flow to the system’s compressor and fan motor.

Without it, your air conditioning system can’t respond to cooling commands. This important part, though small and relatively inexpensive, plays several key roles in your system’s functionality:

• It controls power flow to the outdoor unit.
• It ensures the system turns on and off correctly.
• It protects major components like the compressor from damage.

What Happens When the AC Contactor Is Faulty?

A bad HVAC contactor can cause overheating, short cycling, or continuous operation, all of which lead to expensive system damage. Contactors typically fail in one of three ways:

• If the contactor fails to close, the open circuit won’t allow the air conditioner to turn on at all.
• If the contactor is stuck closed, your air conditioner will run nonstop.
• If the contactor has intermittent contact, your air conditioner will start and stop randomly.

How to Test for a Bad Contactor

The AC contactor is a small component with a big responsibility. When it starts to fail, symptoms can range from minor annoyances to complete system shutdown or expensive damage.

Catching issues early can save you from a bigger repair bill. Homeowners who suspect a bad contactor can follow these simple steps to test for issues safely:

• Visual inspection: Look for burn marks, pitting, corrosion, or melted plastic in the cooling system, as damaged contactors can cause overheating and arcing.
• Listen: Lower the thermostat so the air conditioner turns on and listen for a distinct click. If you do not hear this sound, you may have an issue.
• Check voltage: Homeowners can use a multimeter to verify that their coil has 24V control voltage.
• Test continuity: Use a multimeter in continuity mode to ensure a good connection and strong reading.
• Check voltage across contacts: Check the voltage with a multimeter on both sides of the contactor. If there is a higher voltage reading on one side, the contactor is restricting power.

How to Tell if a Contactor is Bad

Figuring out how to diagnose a bad contactor requires homeowners to pay attention to their cooling system’s performance. Looking for signs of issues can help you get the proper air conditioning repairs done before any serious damage to the system occurs, which may require a full air conditioner replacement.

The AC Won’t Turn On

If you set your thermostat to cool and nothing happens, it could be a contactor problem. A failing contactor may fail to close, preventing power from reaching your cooling system and causing a complete malfunction. This is the most common and obvious sign of contactor failure.

The AC Runs Constantly

If your air conditioner is continuing to run even after your home has reached the desired temperature, call for repairs. Often, a contactor can become stuck in the closed position where electricity continues to flow. As a result, you’ll experience nonstop cooling, higher energy bills, and a greater risk for compressor burnout.

The AC Makes Strange Noises

Unusual noises should always be addressed with HVAC systems. Dirt buildup or worn contacts can result in an inability to engage properly. When the contactor can’t engage, the system may make strange sounds, such as clicking, buzzing, or chattering. This will often get worse over time.

The AC Short Cycles

Short cycling is frustrating for homeowners, as the HVAC system shuts down before there is sufficient cooling, compromising their comfort. This can result from a failing contactor. If it is making inconsistent electrical connections, the air conditioner will turn on and off unpredictably, placing extra strain on the system and reducing efficiency.

Call Brookside Heating & Cooling for Professional AC Repair Services

Having a reliable air conditioner is critical for homeowners in New Hampshire. That’s why Brookside Heating & Cooling offers comprehensive cooling services, including expert air conditioner repairs.

Our team can diagnose and address failing contactors to restore your system to proper performance. With fast response times and available 24/7 care, we prioritize your comfort and safety with services that ensure peak cooling performance.

Plus, if your system is beyond repair and requires a full replacement, we’re here to help you find the right system for your home and needs.
If a failing contactor is impacting your comfort, don’t delay. Call Brookside Heating & Cooling today to schedule air conditioner services with our technicians.