HVAC Repair Tips


The job of your air conditioner is to blow cool air, so when it blows hot air, it means you will have to spend some time in finding the cause of the problem and fixing it. We will begin with simple fixes and move on to difficult ones. Some of those will require the help of AC repair services.

Fixing An AC That Blows Warm Air

Check The Thermostat Settings

You may have checked this already, but if you haven’t, take a look at your thermostat and its settings. Oftentimes, the thermostat is set to “fan” instead of “cool”. So, it blows warm air. Therefore, check the thermostat and make sure it’s set to “cool” and not “warm” or “fan”.

Moreover, also check whether it’s on “auto” or “on”. It must be on “auto” to blow cool air as on “on” it will just keep the fan on.

Inspect The Thermostat

After checking the temperature settings, you should also take a look at the thermostat. A common thermostat issue is related to drained batteries. A sign of insufficient battery power is that the display won’t turn on. Even if nothing appears wrong, you should replace the batteries of the thermostat to make sure the issue is not related to this.

Moreover, when dust forms layers on the thermostat, it can change the temperature sensitivity of the device. This means the thermostat might not trigger the compressor to turn on when required. As only the fan will work in the meantime, it will throw warm air. Therefore, clean the thermostat. Remove its cover and gently clean the parts.

Additionally, if your AC was installed recently and you have been dealing with this warm air issue since installation, the reason could be the wrong location of the thermostat. So, have an expert check it.

In some cases, the thermostat is faulty or not calibrated. This should also be checked by an authorized technician.

Clean The Air Filter

Air filters keep the indoor air clean. By doing so, they keep collecting dust and need to be cleaned. If they are not cleaned, they restrict the airflow, put stress on the unit, and cause various problems like warm air coming out of the vents.

You should also check which type of air filter you have. Disposal filters with plastic frames can’t be cleaned. You have to replace them every time they become clogged. On the other hand, reusable air filters that have a metal frame are washable. The frequency of cleaning depends on how much you use the AC, but it’s a good habit to clean them every 2 weeks.

Ensure That All Return Vents Are Open

It’s a common practice by many homeowners they close vents in winter and reopen them when they require cooling. So, check and open the vents so the AC can maintain airflow for cooling. Plus, check for anything obstructing the vents like furniture, curtains, etc.

Clean The Condenser Unit

Yes, this fix is also about cleaning a part of your HVAC system because many AC problems are merely due to dust and debris buildup interrupting the normal functioning of the unit.

The condenser unit that’s placed outside requires more frequent cleaning because it’s outdoors. As dust and debris build-up, they do two things that make things difficult for the HVAC unit.

One is that dust will cover the condenser coil inside the condenser unit and affect the rate of heat dissipation from the condenser coil. This directly affects the entire air conditioning process and the result can be the AC blowing warm air through the vents.

The second thing is that leaves and debris can block the fan from running properly. The fan is used to speed up the heat dissipation process.

So, if your AC is blowing warm air, you can clean the condenser unit yourself or have the entire HVAC unit cleaned by a professional for proper cleaning. It should be done twice a year.

Check The Condenser Unit For Power

If your entire HVAC system loses power, the AC will not turn on. As it’s turning on but blowing hot air, you should still not rule out power issues. The condenser unit may have lost power due to power cord damage or blown fuse or the circuit breaker that powers the condenser unit has tripped. So, inspect the condenser unit’s power cord, the outlet, and the circuit breaker.

Inspect The Air Handler Unit

The air handler unit is installed indoors and it contains evaporator coils. These coils become cool and as air passes through them to ducts, you feel cool air coming from vents. These evaporator coils freeze due to many reasons like a damaged blower fan, clogged air filter, dirty evaporator coils, low refrigerant, blocked drain lines, and others.

Evaporator coils are sensitive parts of an HVAC system and it’s better to leave even their cleaning to professionals. So, have an expert inspect the unit including the air handler unit, and perform fixes.

Check The Reversing Valve

If you have a heat pump, you should check the reversing valve. Even when the thermostat is set to cooling, if the reversing valve is jammed, your HVAC unit won’t blow cool air. Hire a professional to take a look at the reversing valve.

Clean And Inspect The Air Ducts

The cool air goes through the ducts to reach you. So, if there is a lot of dust stopping the air or a leak, you may not feel cool air coming from the vents. Therefore, an inspection and cleaning of the air ducts may be in order.

You can perform duct cleaning if you have some time on your hands, but inspecting and repairing leaks in ductwork can only be done by an HVAC technician. As you’re not yet sure if the ducts are only dirty or is there a leak, an inspection must be done by a technician.

Look For Refrigerant Leakage Signs

The refrigerant flows through the coils in your HVAC unit and takes part in the cooling process. Any cracks in the coils will lead to refrigerant leakage. As the refrigerant will leak, the cooling ability of your air conditioner will reduce.

If your AC has started blowing warm air and you have checked other things, you should also look for signs of refrigerant leakage so you can consult an expert to fix the leakage and refill the refrigerant.

look for signs like ice on the evaporator coils, water near the condenser unit, hissing or bubbling noise from the condenser unit, and higher electricity bills.

Clean The AC Drain Lines

Air conditioners produce moisture that is drained through a drain line. It should be kept clean so water can be drained easily. If not cleaned, it will become clogged. The water forming due to the refrigeration process will have nowhere to go, so it may leak from somewhere and cause problems like no cooling (blowing hot air). You can clean the drain lines with vinegar or a vacuum cleaner.


Various things can cause an HVAC unit to blow warm air when it should be blowing cool air. Start with simpler things like checking the thermostat settings and the air filter and hire an air conditioning repair service Vienna VA for fixing complex problems.


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