how much to replace contactor on ac unit


What is a Contactor?

A contactor is an electrical switch that controls the flow of electricity in an HVAC system, specifically in an air conditioning (AC) unit. It acts as a bridge between the power supply and the AC unit, allowing the unit to turn on and off as required. When the thermostat signals the AC unit to cool the air, the contactor pulls an electromagnet that closes the circuit and allows electricity to flow into the unit. The contactor is essential for the proper functioning of the AC unit, and if it becomes defective or worn out, it may need to be replaced.

Common Signs of a Faulty Contactor

Over time, especially with regular usage, a contactor can wear out or become damaged. When this happens, certain signs may indicate that it needs to be replaced. Here are some common signs to look out for:

1. AC Unit Not Turning On

If your AC unit fails to turn on, the problem could be due to a faulty contactor. The contactor is responsible for initiating the flow of electricity into the unit's various components, so if it fails to close the circuit, the unit will not start. However, it's essential to rule out other possible causes like a tripped breaker or a blown fuse before concluding that the contactor needs replacement.

2. Unit Constantly Turning On and Off

When the contactor is worn out or defective, it may cause the AC unit to short cycle. Short cycling is when the unit repeatedly turns on and off in quick succession. This issue can strain the AC unit, decrease its efficiency, and lead to increased energy consumption. If you notice your AC unit is frequently cycling on and off, it's best to have the contactor checked and replaced if necessary.

3. Strange Noises

Unusual sounds coming from your AC unit, such as buzzing or humming, can be an indication of a faulty contactor. The contactor uses an electromagnet to close the circuit, and if it becomes worn out or damaged, it may produce strange noises. It's essential to address these sounds promptly, as ignoring them could potentially cause further damage to the unit.

4. Burn Marks or Physical Damage

During regular maintenance or visual inspection, if you notice burn marks or physical damage on the contactor, it is a clear sign that it needs to be replaced. Burn marks can indicate overheating of the contactor, which could be due to excessive wear and tear, an electrical surge, or a manufacturing defect. Physical damage, such as bent or warped contacts, can prevent the contactor from functioning correctly and must be addressed.

5. Inconsistent Cooling

A faulty contactor can result in inconsistent cooling performance from your AC unit. If you notice that some rooms or areas in your home are not cooling as they should, while others are overly cold, the contactor may be to blame. In such cases, the contactor may not be allowing the compressor or fan to function properly, affecting the overall cooling balance.

Replacing the Contactor: Hiring a Professional or DIY?

Replacing a contactor on an AC unit may seem like a simple task, but it involves working with electrical components and can be potentially dangerous if not done correctly. Therefore, it is generally recommended to hire a professional HVAC technician to handle the replacement. HVAC technicians have the necessary skills, knowledge, and equipment to safely replace the contactor and ensure the AC unit functions optimally.

Why Hire a Professional?

1. Safety First

Safety should always be a priority when dealing with electrical components. HVAC technicians are trained in handling electrical systems and follow proper safety precautions to prevent accidents or electrical hazards. They possess the expertise to navigate complex wiring and ensure all connections are secure and properly insulated.

2. Correct Diagnosis

While a faulty contactor may seem like the obvious culprit, there could be underlying issues affecting the AC unit's performance. HVAC professionals have the expertise to diagnose any additional problems accurately. They can identify other potential causes of AC malfunction and address them accordingly, avoiding unnecessary costs or future breakdowns.

3. Warranty Considerations

If your AC unit is still under warranty, attempting a DIY repair or replacement may void the warranty. Manufacturers often require professional installation or repair to ensure the warranty remains valid. Hiring a professional not only guarantees the contactor replacement is done correctly but also helps protect your warranty, saving you from potential expenses in the future.

4. Time and Convenience

Replacing a contactor may seem like a straightforward task, but it can be time-consuming, especially if you lack experience in working with electrical components. Hiring a professional HVAC technician frees up your time and ensures the job is done efficiently. Additionally, professionals have access to the necessary tools and equipment required for the replacement, making the process quicker and hassle-free.

Cost Factors to Consider

The cost of replacing a contactor on an AC unit can vary depending on various factors. Here are some considerations that can affect the overall cost:

1. Contactor Type

Contactors come in different types and sizes, designed for specific AC units. The cost of the contactor itself will depend on the make and model of your AC unit. Higher-end or specialized contactors may be more expensive than standard ones, affecting the overall replacement cost.

2. Brand and Quality

The brand and quality of the contactor can affect its price. Established brands with a reputation for reliability may have slightly higher costs. It is recommended to choose a contactor of good quality, as it will likely be more durable and have a longer lifespan.

3. Location of the Unit

The location of your AC unit can impact the complexity of the replacement process, thus influencing the overall cost. For example, if the unit is in an easily accessible location, the replacement may be simpler and less time-consuming. However, if the unit is located in a tight or hard-to-reach area, additional effort and time may be required, potentially increasing the cost.

4. Labor and Service Charges

The labor and service charges of HVAC professionals can vary based on their experience, location, and company policies. It is recommended to obtain multiple quotes from different professionals to compare prices and choose the most suitable option for your budget.


The contactor is a vital component of an AC unit, allowing for the efficient flow of electricity and proper functioning of the system. If you notice any signs of a faulty contactor, such as the unit not turning on, inconsistent cooling, or strange noises, it may be time for a replacement. While it may be tempting to attempt a DIY replacement to save costs, it is strongly advised to hire a professional HVAC technician for safety, accuracy in diagnosis, and warranty considerations. Replacing the contactor will ensure your AC unit operates optimally and provides comfortable indoor temperatures even during the hottest summer days.


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