What is the best way to clean outside central A/C unit?

Ann J
by Ann J
My HVAC man used a special spray followed by a hose rince. Is this special spray cleaner available to the public? He charged way too much to do this.
  11 answers
  • The spray they use is a foaming cleaner. They use this because once it is sprayed onto the unit the foam expands into the thin areas between the fins of the units coil. Any good quality foaming cleaner would work. Even the foaming product you use in the bath. Anything you purchase over the counter will not harm the metal or rubber materials that it will come into contact with so there is no worry on that front for you. As far as what they use. It is typically a concentrate cleaner that they purchase in one or five gallon jugs. It would way to expensive for them to use the small spray type cans to do this job. Besides needing two or three cans per unit, it would take several more min to apply. And in their business time is money. The most important thing to remember when doing this. Is not to damage the fins with to high a water pressure. They can bend over very easily. They do make fin combs just for the repair of these but not a fun thing to correct once damaged. Another thing to remember is turn off the power at the inside panel when doing this. Both to prevent any possible electrical shock should water get into a area its not designed to do, but also to prevent the water from blowing back into your face should the unit turn on when your cleaning it. If your unit is or has been cleaned within the past few years and unless you live in a real dirty area you really do not need to use detergent to clean the coils. Simply taking your garden hose once and a while when your watering the lawn or washing the car hose it down. You do not need to go overboard every time, just need to get the fine dust off. Cleaning using chemicals is really done for much older units that work in an environment that is real dusty such as homes located on busy streets or yards with lots of activity on them. A simple rinse is really all that is needed.
  • Sherrie S Sherrie S on Dec 30, 2011
    Since air conditioners are expensive and there is more than cleaning to keep an air conditioner in good condition I prefer a moderately priced contract that covers all of the equipment.
  • Sherrie having a service contract is simply a waste of time if your willing to do simple service yourself. That service is changing the filters and keeping the outside system clean. That is all there is to it. Having a service professional in once a year to check the charge in the system only shortens the life of the equipment. Your cooling system is no different then your household refrigerator in the kitchen. When was the last time you had someone come in and check the charge on that? The only service your fridge needs in not much different then your whole house AC system. Clean the dust out of the coils and keep the inside clean as well. One must understand the refrigerant within the cooling system does not get used up. Its, assuming your system was installed correctly in a hermetically sealed environment. Nothing comes in, nothing goes out. By introducing the refrigerant gauges into the system, the service professional also introduces any contaminants that may be present within the hoses that he connects to the system to check the charge. I taught this very subject in our local Voc Tec school for many years. And this issue always came up in class discussion. So as an experiment I had the school purchase a new self contained cooling system direct from the factory. Part of this new system was to have all the test equipment installed in the factory as well. So there was no need for the student to connect or disconnect anything. Just simply evaluate the readings and make decisions on what is wrong or not. The class project was to have all students break down to teams of two. I told them that I was the customer and that the system did not appear to be keeping my house cool. I gave each team 30 min to look system over and put into writing what they think or know is wrong and what they would do to solve it. Mind you that I did nothing to the system. They did not know this. But every team except one told me different things were wrong and what they would do to service the system to make it work better. The fact is that nothing was wrong, they simply did not understand how to read the charts and tools that would have told them nothing was wrong with the system. The moral of the story is even if you get the system serviced and they connect their equipment into the system. It does not mean they understand anything that they are seeing and will change the charge almost every time they come out to visit the home. Read your past invoices. My bet is that they list adjust the charge somewhere on the ticket.
  • Sherrie S Sherrie S on Dec 30, 2011
    Woodbridge. I have the inside and outside equipment checked twice a year. The cost is just $145 a year & I get a discount if I need to make a service call. However, I have never needed a service call. I buy the equipment from them & they maintain that brand. I do appreciate your thoughts.
  • Use a product called Krud Cutter....(purple is the color of the product, the all purpose form) it is sold at Lowe's in a concentrated form. I use it when pressure washing most anything I clean. When my external A/C unit was serviced (by a friend), he used the foaming stuff as well. When I brought him the bottle of Krud Kutter, he stated it probably would work just as well. A gallon is about 12.00, and makes 20/25 gallons. I cut it 50/50 to insure its worth, and it does a remarkable job.
  • Ricardo B Ricardo B on Jan 05, 2012
    Just remember, Ann, that those outdoor units were built to be exposed to the out of door environment. My OPINION... Unless you have the unit in an area that has been perversely neglected or in a very shady area exposed to harsh chemicals, runoff water or sewer/gutter runoff seepage... try just using a pressure washer at about 1200 or 1300 PSI. Use NOTHING but the power of the spray. That may solve your problem with yearly use and you can save bunches of bucks. The Big Box DIY stores sell compact and easy-to-use electrical power washers at under $150. You'll quickly learn that they can also accomplish many tasks around the house, driveway and sidewalks as well as composite siding.
  • I would steer clear of the power washer Ricardo, it does not take to much pressure to bend the fins. When we go out to clean a coil, we just use a real good spray head on the garden hose and that usually does the trick nicely. But your correct usually only the water alone will keep the unit clean enough. We always tell our clients that when their using the hose in that area of the yard, to take two min and simply hose it down. Mostly to keep the grass clippings off of the unit as this is usually what plugs them up.
  • My business started six years ago pressure washing, as well as home repair. Today I have commercial equipment that will put a hole in concrete if I wanted to. I have machines (that I walk behind) that clean horizontal surfaces in a quarter of the time. Therefore, I would strongly NOT recommend using any type of pressure washer on the external A/C unit of your house. If you buy the type of pressure washer that I use, someone who is not experienced can do some major damage to what they are trying to clean, and more importantly harm to themselves. The lower end pressure washers that you can buy at most home improvement stores are not of good quality, and their lifespan is very short from an hour perspective. For instance, if you buy an inexpensive version (150 - 300 dollars) they have a life span of 12-25 hours. This may not seem like a lot, but if you use them for 3-4 hours at a time, this will last you a few years. But, the higher the power of pressure washer, the better the job will be. I know this sounds biased, but leave pressure washing to the pros and allow a bit more space in your garage or storage area for that equipment that gets used once or twice a year, if that. I agree with Woodbridge that ANY type of pressure washer will probably damage the fins of the unit.
  • Exactly my point Straight Nails. In fact many of the electrical units they sell are no better then just using a garden hose with a good quality spray head attached. They just look fancy and provide a method of delivering soap to the object being sprayed. And that can be done with a garden sprayer if need be.
  • DORLIS DORLIS on Nov 29, 2015
    My unit is in a semi shaded area so I will stick with a hose, don't want to be replacing the unit. Thanks a lot.
  • Deb K Deb K on Mar 11, 2023

    Hi Ann, hope this helps you out.