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How to Flush an A/C System

How to Flush an A/C System

How to Flush an A/C System

You may have heard about maintenance services that clean out certain systems in your sedan, SUV, pickup or minivan, such as a coolant system flush or engine flush. There are times when flushing an A/C system is necessary. A car A/C flush is an advanced project, which requires special tools and equipment, so it isn’t a task for the novice DIYer. But, if you have a good grasp on your repair skills and a well-stocked shop, the task is fairly straightforward. Here’s how to flush car A/C system components:

What is a Car A/C Flush?AC flush kit

Car A/C flush is simply a strong specialized chemical designed to clean the inside surfaces of your vehicle’s air conditioning system. It is only designed for cleaning out the A/C lines and A/C evaporator. You cannot use A/C flush to clean components like the expansion valve, A/C compressor or the receiver/dryer. Most modern A/C condensers have extremely compact and complex internal passages, which you cannot flush. Do not flush lines that contain a filter or muffler. So, if you are wondering how to flush a car A/C condenser, the answer is you don’t.

Why Perform an A/C Flush?

If the A/C system suffered catastrophic compressor failure, an A/C flush always needs performed. Depending on the damage, small pieces of metal from the compressor may end up in the A/C condenser or A/C evaporator that you cannot remove via an A/C flush, thus requiring component replacement. It is unwise to not perform an A/C flush and run the risk of damaging a new compressor via debris from the old one. Also, if an A/C system has sat open to the atmosphere for a long time waiting for repair or restoration, it is wise to start with a good internal cleaning.

A/C Flush Tools and Supplies Required

You probably already have a well-stocked toolbox, but you will need a few more things to flush automotive A/C system components:

Depending on your project you may also need:

How to Flush an A/C System

The following is a generic description of the A/C flush process. Your particular vehicle may vary, so refer to your repair manual. But, if you need to know how to flush a car A/C system at home, here are the typical steps:

  • Always work in a well-ventilated area. Ensure the engine is cool to prevent accidental flash ignition of the flush chemical from a hot engine component (like an exhaust manifold).
  • Disconnect the battery and cover both terminals to prevent any accident sparks from tools. The A/C flush chemical is highly flammable and partially aerosolized during the procedure. The flush kit bottle is also usually made of metal, so you want to reduce the risk of accidentally creating a short.
  • If the A/C system is still charged, evacuate it using an A/C recovery machine. Your local NAPA Auto Care center can also evacuate the system for you. Do NOT vent refrigerant to the atmosphere.
  • Reference the repair manual and disconnect each component that needs flushed one at a time. Depending on your vehicle, you may need to remove several other engine compartment components in order to access the A/C components. 
  • Read and understand the directions included with the car A/C flush kit. Most A/C flush kits operate via compressed air at a specific air pressure, so you may need to adjust your compressed air regulator.
  • Fill the flush kit bottle with the appropriate amount of flush chemical stated in the instructions. Wear gloves to protect your skin as the flush chemical is a powerful cleaning agent.
  • Connect the flush kit tool to the A/C component you are flushing. For A/C lines, place the open end of the line in a bucket to catch the flush chemical. When flushing an evaporator, use the outlet connection so that the flush travels the opposite direction of the refrigerant. 
  • Open the valve on the flush kit tool and spray the flush chemical through the A/C component in short bursts until the flush kit bottle is empty.
  • Capture the flush chemical from the inlet connection in a container. You can temporarily attach a length of old heater hose to the A/C component to help direct the discharge.
  • Repeat the flush technique until the discharge chemical from the component outlet is clear.
  • Once a component is flushed, continue to blow dry compressed air through it for 30 minutes to completely remove any leftover A/C flush chemical. Do not skip this step as A/C flush chemicals can harm other A/C components.
  • Reconnect the now flushed and dried A/C components. 
  • Reassemble any engine compartment components removed for access.
  • Recharge the A/C system with the correct amount of refrigerant.

Make sure to check for leaks with an electronic refrigerant detector to verify the system is sealed.

Let the Pros Handle Your A/C Flush

Flushing a car A/C system is not your ordinary DIY job, but it isn’t an impossible task. The goal is to restore a clean, free-flowing refrigerant path that is clean from contaminants. Working on an automotive A/C system requires careful preparation, detailed research, dutifully following procedures and placing safety above all. 

For most vehicle owners, letting the experts at your local NAPA Auto Care handle a car A/C system flush is the right solution. Expect a car A/C flush cost to range between $150 and $500 depending on the vehicle. Use our handy auto repair estimator tool to plug in your specific make and model. A/C repairs are sometimes challenging and time consuming, so letting someone else handle the job can make sense. 

On the other hand, if you are looking for a challenge or an excuse to buy more automotive tools and equipment, make sure to do your research before lifting a wrench. Then head to NAPAonline or your local NAPA Auto Parts store for everything you need to get the job done. Don’t forget to sign up for NAPA Rewards to get one Point for every $1 you spend. Once you earn 100 points, you receive $5 off your next purchase automatically!

Photo courtesy of Pexels.

Brian Medford View All

With an automotive writing career spanning over two decades, Brian has a passion for sharing the automotive lifestyle. An avid DIYer he can usually be found working on one of his many project cars. His current collection includes a 1969 Olds Delta 88 convertible and a slant-6 powered 1975 Plymouth Duster.

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