Your HVAC troubleshooting checklist.


Your HVAC system is delicate. But not so delicate that you can't play process of elimination when the heat shuts off. Here's how to troubleshoot your HVAC system. 

1. Reset the circuit breaker. 

You can make toast, watch TV and blow dry your hair at the same time without starting a fire — and that’s because of your circuit breaker. When electrical wiring has too much current flowing through it, your circuit breaker cuts the power before something surges, sparks or starts a fire. Basically, your circuit breaker is your home’s first line of protection when equipment goes haywire. 

Your air conditioning system has a lot of wires and its own switch on your circuit breaker. So if your circuit breaker trips, your AC will shut off. When this happens, hit the reset button (or switch) on your circuit breaker, and your AC and heating systems will come back to life.

If your circuit breaker keeps tripping, odds are you have a more serious problem. Either your circuit breaker needs to be serviced or your AC has larger electrical system needs. No matter which it is, it’s time to bring in a professional.

2. Check for frozen or damaged coils.

If your AC system isn’t blowing cool air, check to see if your coils are leaking, frozen or damaged. Frozen coils can occur when:

  • Refrigerant is leaking.
  • The thermostat isn’t working properly.
  • Temperatures drop and the air can’t move freely across the evaporator coil due to dirty air filters, broken fans, duct issues, etc. 

Changing your air filter, cleaning coils and defrosting your unit may help unfreeze your coils. If those steps fail, you may need a technician to find the source of the refrigerant leak and repair it. They may also need to fix your ducts or thoroughly clean your coils. 

3. Clean dirty condenser coils. 

Your AC system has a lot of coils. Here’s how to tell the main two coils apart: the evaporator coil is located inside your home in your air handler (the thing with a fan and an air filter). It’s one of two core components and is filled with a compressing agent that absorbs heat from the air inside your house. 

The condenser coil is located outside of your home in the metal unit. It’s responsible for cooling warm air off with refrigerant and cycling it back into the house. 

Bad things happen when dust and grime build up on the condenser coils in your outdoor AC unit. If the coils get even a little dirty they lose efficiency, causing heat to build up in your compressor. When this happens, your system will shut down. 

Check your condenser coils every few months and wipe them off even if they look clean. Even a thin layer of dust can cause you real problems in the long run. 

4. Check the air filters.

It might look simple, but that rectangle sliding in and out of your HVAC system is actually doing a lot of work all the time. Before you breathe it in, the air that circulates in your air conditioning and heating systems gets pushed through a densely woven screen of fiberglass and cloth to clear it of mold, dander and other hazardous materials.

Your furnace filter protects your furnace (and the blower fan) from the dust, hair and dirt in your duct system. If it’s clogged, it can cause malfunctions, block airflow, dirty your air ducts and negatively affect the air quality in your space. 

Cleaning your filter out between seasons will keep debris from building up — and save you a maintenance bill. Check your air filter every other month by shining a flashlight through it. If you can’t see light on the other side, it’s time to put in a new one.

5. Check your blower motor for dust and overheating. 

Your air conditioning system is controlled by fans with motors that can break, get jammed and fail. The two main fan motors to know are the blower motor that pushes air around the inside of your home (through vents and ducts) and the air conditioning condenser that cools off warm air that’s been pumped in from the inside of your home.

If your motor stops working, your AC and heating systems will too. To do some basic troubleshooting, check under the cover of the motor for any signs of dust or overheating — both of which can cause your fans to shut down. 

6. Check the outdoor air conditioner unit’s foundation.

Let’s talk more about your outdoor unit, which has two parts — a compressor and a heat exchanger — installed just outside of your home on a concrete slab to keep it level. The most common air conditioning unit problems usually have to do with the concrete slab underneath. If the ground beneath the concrete sinks, the unit on top of it will be thrown off balance. That means damage to your central air conditioning system.

Stay ahead of problems by checking your AC unit regularly for signs of sinkage (especially between seasons, when the ground is soft), and correct the leveling ASAP where and when gravity hits. If you don’t want to do this, you can hire an HVAC technician to come out every few months to inspect it for you.

7. Check the control board and thermostat settings. 

Most home systems have a user-friendly control post. For your HVAC system, that’s your thermostat. Depending on how it’s programmed, your thermostat might not be operating at peak efficiency (ie. it’s set to keep your home warmer or cooler than it has to be). It’s also possible for your thermostat to go out, making it impossible to use.

If you’ve checked the batteries and your thermostat just isn’t working, hire a professional to install a new one. 

8. Make sure all the registers in your home are wide open.

Registers control the airflow from your heating or cooling system into your home. It’s a grate-like metal plate that covers a vent opening.

If you don’t feel any air but your thermostat is on, check your register. If the grates are closed, it’s as simple as opening them back up to let the air in. Easy, right?

When to DIY vs. hire a professional for HVAC issues.

If you’re comfortable with performing small maintenance tasks, such as changing the filters or cleaning the coils, the DIY route may be right for you. But if not (or if your DIY fixes aren’t working), get a professional’s help. An HVAC technician can troubleshoot or repair your home’s heating and air conditioning systems. 

Professional air conditioning maintenance and repairs cost $50-$100 an hour, on average, though expect to pay about $300 in parts and labor. Most companies charge a flat rate to cover the repairs needed after inspecting a system in person. And as a rule, the older the unit, the more expensive a repair will likely be. 

The best way to keep your AC and heating system working efficiently is to change the air filter at least once a season. Keeping your air filter and condenser coils clean and free of debris can help lower utility bills, too. 

Related: How much does air conditioning repair cost?

Who to hire to help with HVAC troubleshooting.

Hire someone to keep your home’s temperature in check, inspect your vents and make sure the air you’re breathing is clean. Here's a list of pros who can help you troubleshoot and/or repair:

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