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Eventually, every car’s AC system fails, which can introduce contaminants and debris.
The only way to prevent this contamination from spreading is to flush the system while lines are open.
Fortunately, flushing the lines is easier than most people think. It does require a couple of special tools, but it is a vital step in most major AC repairs.
Key takeaways
What exactly is an AC flush?
An AC flush is the process of cleaning the aluminum lines and the coils to remove any dirt or debris trapped inside.
Unlike a periodic coolant flush, a car’s AC system doesn’t need flushing unless a major component fails.
Why do car AC systems need flushing?
Car AC systems need flushing because small pieces can break off and clog the lines when a major component fails.
Thus, any of these contaminants could cause further damage.
How to tell that your car AC needs flushing?
There isn’t a definitive way to know that an AC needs flushing.
With that in mind, I would flush the lines when replacing a major component, such as the compressor.
How to flush car air conditioner in easy steps
Flushing a car AC system isn’t overly complicated, but properly removing the refrigerant and disassembling the entire system can be complex.
The steps below outline the entire process and what to look out for along the way.
Things you’ll need
Performing an AC flush requires a handful of specialty tools.
Since most people don’t have these items lying around, auto parts stores often loan them out for free.
Recover the refrigerant
The first step for flushing an AC system is recovering the refrigerant in the system.
To do so, connect the hoses from the recovery machine to the respective service ports. Pump the old refrigerant out of the system and into a recovery tank.
Evacuating an AC system does require an EPA Section 609 certification, which is easy to complete online.
After completion, it also allows the cardholder to purchase larger refrigerant canisters.
Never vent freon into the atmosphere, as it is illegal and dangerous. Additionally, the cold refrigerant can cause burns.
I would visit a local auto service center to see if they will evacuate the car’s air conditioning system.
This is a great option since the equipment can be expensive for someone not doing AC work regularly.
Replace faulty part
With the freon out of the air conditioning system, it is safe to open the lines.
Before flushing the lines, I like to remove the part that failed.
The AC compressor is the most likely reason someone would perform an AC flush, since its moving parts often break off and damage other components.
Replacing an AC compressor is usually straightforward, but it can be tedious depending on its location on the engine.
Clean the evaporator
The best place to start the flush is the evaporator coil.
This component is actually inside the dashboard on most vehicles. However, its lines are accessible under the hood.
Clean the AC lines
Next, I move on to the AC lines that run throughout the system. I disassemble all the lines from the remaining components, including the condenser and dryer.
I also try to keep the lines organized so I know how they go back together. These lines can house accumulators, which should be replaced.
With everything disassembled, I blow out one line at a time while still trying to flush them in the opposite direction of the refrigerant flow.
Replace the condenser
Once all the lines are flushed, I move on to the condenser. I recommend replacing the condenser coils on most vehicles because they are pretty cheap.
The reason is that the condenser contains many small passages, which are nearly impossible to clean.
Identifying and eliminating blockages that could circulate and cause further damage to the new parts is also difficult.
Sometimes, there are no choices other than cleaning out the condenser. Some coils are very expensive or hard to find, which is when flushing becomes an option.
Because AC flush kits are expensive, I recommend a cleaner that uses compressed air rather than an aerosol can.
Small coils are also much easier, as larger coils could take several cans of flush to fully clean.
Removing the condenser is very time-consuming because it is attached to the radiator.
Depending on the vehicle, the coolant may need draining before removing the entire assembly.
Replace the AC accumulator/dryer
With the condenser out of the way, there are a few minor components that should always be replaced.
I already noted AC accumulators in the lines should be removed. However, the dryer also needs replacing anytime the lines are opened.
Getting contaminated refrigerant out of these parts is nearly impossible, so it is best to get new ones.
With all the lines disconnected, I have to unbolt the dryer from the firewall and bolt the new one in.
If there is no other choice, then circulate the flush through each component to clean them out as best as possible.
However, this is a major risk that could lead to a bad experience down the road if all the debris doesn’t come out.
Blow out leftover solvent
I don’t reassemble any of the components immediately after flushing, so each part has a chance to dry out.
After cleaning everything, I return to each part and blow it out with compressed air.
Blowing parts out isn't to remove any contaminants or blockages, but it will help remove any leftover solvent from the lines.
After blowing them out, I give the parts ample time to air dry.
Reassemble everything and pull a vacuum
Now that all the solvent is out of the lines, it is time to put everything back together.
I start at the condenser and reinstall it, as well as the fan and any other components that had to come out.
Related article: How to find and fix a car AC leak?
Recharge the AC system
Finally, it is time to recharge the system with refrigerant.
All this requires is the same set of gauges used for pulling a vacuum, along with an adapter when using small cans.
ACLAB note:
One mistake people often make is buying freon with oil or other additives.
Since I already added oil, I don’t want to add anything else to the vehicle. Reading the label is critical to ensure the can only contains refrigerant.
Cars have a specified amount of refrigerant they need. This amount is noted in the service manual and can help gauge the number of cans needed.
However, adjusting that a bit is common based on the gauge readings and proper pressures.
FAQs
How much does it cost to get your car AC flushed?
The cost of an air conditioning flush is highly dependent on the make and model of the vehicle, but it can also vary by region.
Assuming other work is done, an AC flush can be as low as a couple hundred dollars or exceed a thousand. The price of the necessary parts, such as the coil and dryer, will also affect the price.
Can I flush the AC system with water only?
Doing a DIY car AC flush is possible, but you cannot use water. Water can cause serious damage to a car's AC system if all of it doesn’t come out.
Instead, I would use an aerosol can of AC flush for a DIY job.
Does coolant flush help AC?
A coolant flush doesn’t help the AC. Many people confuse a coolant and an AC flush, but they differ significantly.
The coolant flush removes contamination in the radiator rather than the air conditioner. However, a radiator flush should be performed as part of regular maintenance every 30,000 miles to remove debris and dirty fluid.
How often do you need to flush your car's air conditioner?
Unlike a car’s coolant system, the air conditioning does not need to be flushed regularly. It should only be flushed when replacing major components.
Should I flush the AC when replacing a compressor?
I would flush the AC when replacing a compressor because it is a lot of time and money to risk.
Performing a flush is a good way to ensure that your car’s air conditioning stays operating efficiently for years to come.
