A Basic Clean for Outdoor AC Units




With summer approaching soon comes the time to turn on the AC to keep the house cold. You might notice that your electric bill spikes up more than expected or that your house is just having trouble staying cold. If it's been more than a few years sense your last AC unit cleaning (or you cant remember ever having them cleaned) then its probably time for a clean. It's a fairly easy process so save some money by doing it yourself!

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Step 1: Safety First

Whenever doing ANY work with electronics its important to turn the electricity off and check voltage on the unit with a multimeter. Again, DO NOT WORK ON LIVE ELECTRONICS. For this particular project the risk isn't as much to do with shock (though this still exists and adding water to the mix is even more reason to be cautious) but more to do with fear of the unit turning on and spinning fan blades. Most units should have an electronics box near the unit on the outside of the building. Open it up and flip the switch to the OFF position.

Step 2: Tools and Equipment

The tool list for this project isn't a long one. A ratchet set, flat head screwdriver, a multimeter, and maybe a mallet are all you will need. I prefer using a ratchet set over the flat head simply because I find flat heads tedious to use.

Step 3: Disasemble

The metal shielding surrounding the unit needs to be removed. Go around the unit removing the screws holding the shield on and once they are all removed it should come off with little trouble.

Step 4: Clean the Unit

Using a garden hose with low/no pressure spray the outside to remove buildup of dust, dirt, leaves, and whatever else is stuck on the side. The units pictured are extreme examples of buildup. Much less buildup can still cause issues in cooling. Start by spraying off the outside at an angle and the buildup will come off in a 'Peeling' fashion. Then finish up by spraying from the inside out to clean out debris stuck within the fins. (When the buildup is high the fins wont allow enough water to get through to effectively clean the outside without first spraying the outside) While the unit is open I clean out any debris that has built up at the bottom of the unit. Continue spraying around until the unit appears clean. Use very low pressure to avoid bending fins, just an open hose end should do.

Step 5: Reassemble and Cleanup

All that's left is putting the unit back together, cleaning up, and turning the electricity back on. You should notice an improvement in cooling in your house and you didn't have to spend $100+ to get it.

Step 6: Notes

Final notes: Not all units are the same. This second unit pictured is different in that the side shielding is "capped" by the top piece instead of screwing into the side. Your unit will more than likely differ slightly from the two pictured but the concept is the same regardless of the unit.

Also, this is a very basic cleaning of the units. It will improve efficiency greatly in the unit. However, a good professional service will be much more thorough.

Read comments below for additional ideas anddiscussion

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    42 Discussions


    Question 1 year ago

    It's OK to spray at wiring or at condenser section?


    3 years ago

    I really appreciate the time taken to write this informative post. Regular maintenance of electronic device is really important, having an annual air conditioning repair and cleaning services of professionals such as estesair.com, http://www.amtekair.com/ and many others can keep your system work more efficiently working for long duration.


    3 years ago

    Now, everyone go take your units apart... I need the extra money.


    4 years ago

    No No No! First of all as a HVAC technician you learn to never trust the breaker. I see it from time to time that you turn off the breaker and the unit still has 240 volts or more. This Instructable is not recommended for people who don't have a good understanding of electricity. The condenser fan has enough power to slice off fingers or break an arm or wrist. Also throwing water into the mix your asking for an accident. We USE multimeter's to double check the power is off.

    The condenser fan blows upward sucking dirt, grass clippings, and other particulates into the coil from the outside in. So you spray from the inside out to flush it out and not lodge something in deeper.

    To do this we generally take the top or the fan off. Problem is that the wires go to the contactor and to a capacitor. There's a possibility that contactor has 208+volts, and the capacitor can still deliver a massive shock even if the power is off since it can store a charge. Again a multimeter is a must and good understanding of electricity. When your putting the fan back in make sure there are no loose wires to get caught in the fan; use zip ties.

    Also the use of caustic sprays to clean condenser coils are not recommended because it can potentially strip protective oxide finishes causing the metal to further deteriorate. Not to mention if you don't completely rinse it off that too will eat the coil. The caustic coil cleaners are designed for your evaporator where the metal is thicker and condensation will further rinse off anything you might have missed.

    In order to prevent breaking your warranty use a solution of simply green or a detergent to clean really dirty condenser coils and stay away from acids and bases unless it's your evaporator.

    And OMG no, you don't need a ratchet set and god forbid a mallet. First and foremost you need a multimeter, set of nut drivers, needle nose pliers, Flathead/Phillips screwdriver, and some zip ties to tuck away extra wires. I'm considering making my own instructable where I'll show how to clean and check all the component to make sure nothing will break down in the summer.

    8 replies

    Reply 4 years ago on Introduction

    I have something better, as far as safety. I stood over my A/C installer and demanded they install a 240 V AC plug on the A/C unit, that plugs into a socket on the breaker box. Now when I need to do repairs or maintenance, I can unplug the unit and know it's dead. This is the same form of safety that is routinely performed when repairing vacuum cleaners, power saws, and the like. I am not comfortable working on any equipment that is hard-wired to the line through a box. One bump of a lever, or a sticking switch, and you're live! I have never seen electricity "jump" through a plug that has been pulled!

    Before the wet cleaning is performed, a shop vacuum should be used to remove leaves and other dry matter, both inside and outside the unit.


    Reply 4 years ago on Introduction

    Im surprised your installer obliged as that is against electrical code and would be failed by any inspector. A/C units are to be hard wired, Just as hot water heaters are, with a means a of disconnect, within sight.


    Reply 4 years ago on Introduction

    It is not against electrical code. The installer put in the disconnect box as usual, per code, but instead of hard-wiring the A/C unit, he put a socket in the cutoff box, and a cord/plug on the A/C unit. Read the rest of the comments on this subject! The first thing that is repeatedly mentioned is don't trust the cutoff switch! (I have seen one pole fail to disconnect because it rusted out). A plug, when removed, can always be trusted! I demanded the same for a bandsaw at work.


    Reply 3 years ago

    Yeah, its against code, and no creditable installer or company would do that. Key word there is creditable.


    Reply 4 years ago

    That is 100% against NEC and would fail an inspection. I have never seen an disconnect fail. The approved disconnects actually remove the contacts from the box creating a visible air gap.


    Reply 4 years ago on Introduction

    I've got to agree with you 110% as I noticed many of the things of you pointed out. I like this site for "ideas" but that sad fact is many people either give wrong instructions that could cause someone to damage their equipment, items, etc. or simply give instructions that are against code, or flat out dangerous. I notice this especially on projects that have electricity, building something that uses electricity, or adding extra electricity to something, etc. etc. Maye one day I'll have the time to go through everything electrical on this site that's done wrong, and do a write up with the correct way to do it. LOL!


    Reply 4 years ago on Introduction

    As I mention in mu 'ible I just use water and no corrosive cleaners. This is intended to be a basic cleaning that most people can do at home to improve their cooling output and not as instructions on a full professional service. I appreciate your comment and I'd love to see an instructable on how to do a full service. As for my choice of tools; I prefer a ratchet to a flat head because of convenience and a rubber mallet is very handy when trying to get the top back on on 'Lid' style units. If you do not need a mallet then of course thats fine. I just happened to find it useful so i mentioned it as an optional addition.


    Reply 4 years ago

    I apologize, if it works for you use it by all means there is no right way.

    As far as simple things anyone can do easily would be to visually check the contactor. It shouldn't be pitted horribly from arcs. It sometimes has a plastic cover that's held in place with a small Phillips. But be cautious as the thermostat wire supplies 24v even when the breaker is off. Its not deadly just annoying.

    Also visually checking the capacitor for any obvious problems. (silver & cylindrical or oval with wires coming out the top. It should not be bulging or leaking a oily substance. Without a multimeter you can't really test it, but if you see any of the above problems get someone to replace it.

    Also keep a eye out for dark/dirty stains on the condenser fins, by the service ports, on the cement the unit is on. If there's a freon leak it indicates it by sprays condenser oil in the vicinity.

    I am an electrician and follow the NEC and have read some of the comments about safety. I always turn of the 30A breaker at the electrical panel. If you don't know which one it is maybe you shouldn't be doing this at all. Everyone needs a good HVAC person. Ours is the best and so I know it's safe because he does everything the best that can be done. For the guy who was all wet just from cleaning coils and shocked himself....really? What are you doing? The condenser unit releases heat to the outside and doing this to increase the surface area and heat transfer is an excellent thing to do every 5 years. Keep the area around your compressor unit free of leaves and dirt and plants that block airflow. The pictures of the person who did this instructable show otherwise. His compressor space is full of leaves. Put down large stone or gravel around the compressor, light colored if it is in the sunlight. The sides pull in air so keep them clear. The space straight up needs to be clear for the hot air to be pushed straight up by the fan on top. Be cool everyone!

    When I was an auto mechanic "Spray Nine" was everywhere. I have a Rheem exactly as depicted and sprayed the fins and coils with Spray Nine. I was astonished at how all the grime and buildup of any kind was gone. Shiny! Being a chemist I believe it's safe to the hardware. Be careful when taking off the cover! There is not a whole lot of structural support for the coils; flex the outer cover away from center and do not hit the fins. The socket driver should be 3/8" (usually yellow handle) for the hex head/slot screws. Let the Spray Nine soak in for the recommended time.


    4 years ago on Introduction

    One other thing is worth mentioning. A lot of the units use aluminum for the condenser piping, and copper for the remainder of the lines. For these units, there are 2 copper to aluminum brazed joints in the outdoor unit. These are subject to corrosion because of the galvanic difference between aluminum and copper, so most units have these joints covered with a "tarry goo". It would be wise to inspect these for integrity, lest they corrode later, and recoat with a corrosion protectant such as LPS3.


    Reply 4 years ago on Introduction

    Acid or Base (caustic) coil cleaners should not be used on condenser coils. Sometimes the manufacture uses a special oxide finish to prevent the coils from "rusting". Thus removing that oxide finish voiding a warranty and degrading the life of the condenser coil.

    You should only use a detergent like dish-soap or simply green and spray from the inside of the unit out. If heavily built up grim let soak for 5-10 minutes, then spray off.

    Coil cleaners are supposed to be for evaparator coils because the fins are heavier duty, and if you missed rinsing any off the condensation will take care of it. But make sure to rinse completly or else the cleaner can start attacking the integrity of the metal.


    4 years ago

    its a good idea to discharge the capacitor. even with the power off it can give you a shock. im used to it but some people might think it hurts.

    2 replies

    Reply 4 years ago on Introduction

    It certainly can! A few years ago I turned off the breaker to the unit, turned off the unit inside, and isolated it electrically outside, then started with the water. It's a messy job, with water splashing everywhere, and pretty soon I was soaked and standing in a puddle of muddy water. Then POW! The capacitor discharged up the water stream, into the hose nozzle, up my wet arm, and down my wet clothes into the muddy ground. The plastic hose nozzle literally exploded. Ever since then I leave the cleaning to somebody else - one big electrical shock at my age is one too many!


    Reply 4 years ago on Introduction

    I find this hard to believe! The capacitor is connected in series with one set of motor coils. This combination is connected in parallel with another set of coils. This is true of both the fan and compressor motors in single-phase-powered units. As soon as power is removed, the capacitors are shunted by the series connection of 2 coils, a handful of ohms maximum each. The capacities are in the range of 10 to 50 microfarads. They would discharge in a fraction of a second! And certainly, the maximum energy stored in them would be totally incapable of blowing up a hose nozzle! I say you were hooked directly to the line, not shocked by capacitor stored energy. Was there a hum accompanying the explosion? A hum would prove this was the AC line, and not a pulse discharge from a capacitor.