Cleaning a HVAC Condenser Coil

Welcome to Israelhvac's KZbin Channel. On this channel i bring you along on HVAC Service calls, HVAC Maintenance and pretty much anything else HVAC related. Enjoy and thanks for watching.

[@rmick66]

Tune in tomorrow for another episode of The Angry Tech.

[@midntdlight4782]

Careful with tje pressure. You dont want to bend a whole row of coil

[@EightiesTV]

Not a big issue with the older 10 SEER units that had flat fins and reasonably spaced around 14 fins per inch. But the newer high efficiency coils have fins that are much tighter and they are not flat. They have little scoops stamped into them with the opening facing the outside to make the air more turbulent resulting in better temperature transfer. These scoops are little funnels and once you push even a little dirt into them, it plugs them good. You won't see it because it's between the fins. I've seen many plugged coils, especially evap coils that were spotless on the faces yet plugged so bad I had to run 4 rounds of NuBrite just to get the air flowing back at rated CFM. That said, you don't get paid more for getting it cleaner. You get paid for getting it done. And this homeowner obviously likes to point the mower discharge at the outdoor unit and not turn off the AC while mowing. It'll look like that again by the end of mowing season. Sometimes good enough is good enough.

[@brendarichardson7271]

*Great and Easy to instal **Fastly.Cool** Low noisy*

[@HVACRSurvival]

On something like that I'd do it the same way but also like to hit it from the inside out to make certain I have a clear stream of water. I use a 3/8" diameter by 4' rigid copper spray nozzle I built to spray the coil from the inside without having to disassemble the whole unit. Basically like the needle jet. Good to see someone else cares about the quality of their work.👍

[@murkyturkey5238]

Probably takes you 2 hours as well

[@HVACRSurvival]

@@murkyturkey5238 ok?

[@murkyturkey5238]

@@HVACRSurvival washing coils is a conspiracy

[@14thabz]

I can honestly say that when I clean any condenser coil, I always spray from the inside out.

[@gatorr4life]

Came here just for this comment. Thx

[@moneyydogg4318]

That’s pretty stupid, you should just spray it from the outside and do it until the water goes all the way through the coil and looks kinda clean coming out the other side

[@jettelo]

THATS THE PROPER WAY. Spray the opposite way that it's collected. So yea inside out. Smart guy. Now. Spray coil cleaner in it so it eats a whole in the lines and you have a leak and have to replace the unit 😂💯😜😉

[@jettelo]

@@moneyydogg4318 NO YOU SPRAY THE OPPOSITE WAY THAT ITS SUCKED UP. if you do it the way you say your clogging the coil. Take a class you will learn

[@VinniePepperoni]

Many older units that has no removable panels over the coils, so ur forced to pop the top and back flush

[@r2ro56]

I THINK THE WASH IS FROM INSIDE TO OUT SIDE FOR BEST RESULT, TRAY IT.

[@voro5102]

looooooolll

[@JASMOOTH26]

Exactly

[@caru3257]

it is not better.

[@johncote2776]

Nice "Sweater" on that unit

[@mychoclabwinston]

Love when I find coils like this, it’s pretty satisfying cleaning them,

[@jarvisgranger5528]

Same here 💪😎

[@thompsonkennels]

Only on commercial units does it matter due to the thickness of the coil or multi layer condenser coils like carrier on there roof top units.

[@aocofficial8834]

I,m enginer from indonesia, HVAC its give me and family live,

[@rigobertogervacio223]

Very nice

[@hansinglauw863]

Pak, ty donk... ini cara semprot airnya sdh benar ya dr sisi luar utk bersihin debunya ? Bukan dr sisi dalam? Mohon pencerahannya. Terima kasih 🙏

[@wtfman5313]

Ive clean coils this way since 1984 and have never had a problem. In fact that's how they taught us to clean coils in school and now all of a sudden it's a problem. Overtime dirt and dust gets pulled in between the coils regardless and it comes out one way or the other regardless. Just keep doing what you do dude.

[@dannysmith713]

It's because of the stacked or double coils. It pushes it in between the two coils the you have to split the coils.

[@jacketofthe80s13]

THEY TAUGHT YOU THAT IN SCHOOL? THEY DIDN'T TEACH US THAT IN HIGHSCHOOL OR AS A KID WTF

[@wokejoke2675]

@Jacket of the 80's most likely technical school for HVAC

[@wtfman5313]

@@wokejoke2675 - Did you catch the part where I said "never had an issue".. I don't do micro-channel coils like that, but older coils I do. If water is passing through the coil, so is the dirt... it's not too difficulty of a theory.

[@wtfman5313]

@@dannysmith713 - Those types of residential units dont have a dual coil.. it's single stage..

[@RealityRenovations]

I wash from whatever way is easier... honestly unless the coil is four inches thick its not going to make a measurable difference. If someone wants to blow an extra twenty minutes dicking around with some of the complete engineering blunders of outdoor units out there, than all the power to them.. but me, I'd rather get the job done and move on to the next one. That being said, in most cases it is easier to pop the top and back flush, than deal with the ridiculous side panels and the way they are fastened.

[@RealityRenovations]

Cough cough.. American Standard

[@AK99581]

That's the way most companies want their techs to work...bang out the job as fast as possible and move onto the next one. I really hate working like that, I'd rather take my time and do a really good job, but I'm not my own boss so I can't do it that way unless its outside of work. My home unit and those of my family get the works.

[@Straight_White_Fatherly_Figure]

Hell i don't even take the panels off unless its a double coil and i still get the job done hahahaha. Some of this extra stuff is too much, dudes love putting on that show for the customer.

[@lilnikletz6102]

The water pressure and angle you hit the coils is something to keep in mind. You will have issues with all your fins bent over

[@deanfoster465]

Looks good to me, I clean units the same way and never had any problems.

[@Straight_White_Fatherly_Figure]

I love when people try to tell you to clean from inside out but i personally can never get them clean doing that lol. Outside in cleans them everytime at ease with no further issues.

[@janicec.9728]

I'm wondering if ... What happen if I don't turn off the unit? The other day I took out the big fuse,then when I put it back didn't turn on. I have to call for service for a short circuit. My a/c have 20 years young. 🤔

[@gregred78]

@@janicec.9728 did you put the disconnect back in the right direction. If you put so in upside-down they won't engage the contacts on the disconnect.

[@saminohio8952]

Theoretically, back flushing the coils might get it cleaner with less water. As a practical matter, it probably doesn’t matter. Either way, you want to see clean water coming through on the other side.

[@s1lvrinferno]

What do you think is behind the coil a brick wall? Lmao I love it

[@celestialdream49]

Would have been nice to see inside the coil housing... maybe prove your "no pushing into the coil" point.

[@MrThree6nine]

Exactly. LOL. He kept saying "see" but we "see" no proof

[@zesty2023]

I honestly love doing the coil cleaning on my checkups, it's one of the most visually rewarding parts of the tuneup if they're really dirty like this. It's so easy but it's making such a big difference for efficiency and heat-exchange.

[@markcostello9483]

Clean starts on the inside....ignoring that fact goes against common sense

[@tonydellapennajr2681]

I personally like to put the cleaner on the outside. Allow to soak for a few minutes. Spray the outside to know all the shit off and follow up by spraying from the inside outward. Adds maybe 5 minutes and i feel confident the coil is clean enough. I also use the flat setting on the hose.

[@TedCookHVAC]

We all have our own ways and opinions however, it would appear your method works very well for you. The key would be on the initial rinse, not to spray straight on and push the dirt inside the coil(like a dummy)... We can see that from an angle like you did, the initial rinse took off the majority of the surface dirt.... then the coil gun took care of the deeper cleaning. Good video in my opinion.

[@jakup10]

I prefer to always hit it with a brush first when it's like that.Knock it right off instead of spraying it deeper into the fins.

[@rob6154]

I'm a HVAC Technician and I've cleaned a lot of coils like this with the coil cleaner and it helps compressor

[@murkyturkey5238]

No shit it helps the compressor 😂

[@THEMOWERMEDIC1]

Hey great vid, put Amazon links in the description and make good money posting stuff you use every day. Tools, equipment , gas, ect. I do, it pays the bills and the. Some

[@masterdirk101]

Coil gun on amazon is like 90 bucks, its 60-70 every supply house I pass buy, bought it at a johnstone for 55

[@kwm380]

How on earth did it get that dirty? Jeez! Nice job.

[@bluesdirt6555]

I’ve seen them next to the dryer vent discharge

[@gregred78]

Looks like grass clippings in it mostly, so I'm guessing that at one point they didn't keep the grass up and were slinging a lot of clippings into it.

[@xraykadiddlehopper8067]

Dam where did all that crud come from? You must live in a pretty bad area because in 7 years my unit has never had that much crap sucked onto the coils. Your breathing that kind of air?😳

[@yepper1165]

If Cottonwood trees grow in the area they get filled with cotton then everything else collects in them too. Dust is always an issue in windy areas. Nebraska gets it all. Best to clean in Spring, midsummer, and fall.

[@ExamineLife4]

As an industrial hygienist, the probability that new growth will re-bloom if the material is just laying on the ground is very high. A lot of that accumulation is mold too; not just dust such as Alternaria Alternata (a dust borne mold causing respiratory issues). And 10% of the population is allergic to Alternaria Alternata in the United States. In Arizona greater than 51% is allergic. Sensitization (allergy obtained) when the individual has been overexposed for a period of time and the immune system writes and exaggerated response to the allergen. Why is Arizona different? They are running A/C more and it stands to reason that the well known reservoir (place this allergen is found) is in A/C coils. It is an established fact that indoor air quality is adversely impacted by HVAC systems which are not frequently cleaned. Kudos to workers keeping up on condenser coil cleaning and filter changes. The kiddos developing asthma and folks struggling with breathing problems need your support. Anyway, just a suggestion, vacuuming with a HEPA vacuum without leaving the bulk debris on the ground might be a good idea to prevent rapid re-growth. However; if the goal is repeat business (wink, wink) homeowners might have reason for removing the tops and going in deeper with the cleaning. Knowing that much of that dust is an airborne mold that causes respiratory issues might influence the approach to cleaning.

[@FG-tg9uk]

"Pump-up sprayers can kiss my ass." If you pay close attention to the liquid being sprayed on the unit, probably 80% of it runs down the coil and onto the ground. I use a "Pump-up" sprayer so I don't waste the cleaning solution. "Coil gun does a really good job." Is it the coilgun or the Nu-Brite? Because Nu-Brite is so strong a cleaner, I've only used it on kitchen units that have grease on them. Did you remove the fan and clean inside the condenser? On a unit like that, I would vacuum it first, so as not to leave a ton of debris on my customer's lawn. They appreciate it.

[@arrosconpollo1]

This is why people diy. Appreciate your expertise but the high pressure appears to be damaging coils and in my are there are leaves and debris that collect on the inside. So to a large degree I have the satisfaction of treating a pretty expensive piece of equipment differently then someone who is concerned about the next job, according to some of the comments, especially for my sister’s house, etc. Great post. I’ll definitely consider your points.

[@nfz4177]

If you use foam based cleaner it doesn't matter which way you wash it because expanding foam will loosen all dirt.

[@nickv4073]

Why wouldn't you brush off what you can first?

[@AK99581]

Thats the way I do it

[@nfz4177]

Time waste

[@markcotter2355]

I believe a professional cleaning that cost money should be done by pulling all the panels including the corners and top. disconnect the wires for the condenser motor and set it aside. vacuum the inside and flush the coil from inside out and outside in. both ways to really clean it. The main reason I clean the bottom out of dirt and leaves is that a few condensers a customer of mine had a very long time and the compressor developed a leak at the bottom where dirt had eroded a hole in the metal. Cleaning the equipment properly is hard and should cost about $200-350 but it is much better than just an outside only cleaning.

[@rustyshackelford9156]

You can tell he is pissed about the pushing it into the coils comment. Lol it is pretty annoying when the keyboard experts start in.

[@noname-gr7lf]

It is not "crap" to say flush outward. You flush outward. Secondly, you need to remove the fan assembly to clean the floor. Job half done! You need to flush outward, and inward, after the inside of the housing is cleaned up.

[@adamsmith8738]

They teach you in school and on the job to clean coils the way this guy is doing it. And not all condenser units have panels on the side, many have open coils you have access to.

[@Bigsteve123]

cameron yogibear this dude is doing it all wrong. It should always be rinse inside to out. And to never use jet stream and not to spray fins at angles.

[@TheMcGuireLife]

Hi, John Israel this is Jermey McGuire. I, had a 5 ton Lennox XC16 air conditioner that cooled upstairs. Back in July 2022 the high pressure switch tripped, we had to get a tech out to reset the high pressure switch. And cleaned the coils and last July my blower Moyer failed.” Had to get the blower motor replaced, unfortunately I had to replace both my downstairs and upstairs air conditioners.” Back on Wednesday 4/1024 Lennox is so expensive!! Just to get a part replaced, to bad Lennox won’t let you use universal parts like Goodman. And Goodman keeps parts in stick, then having to call the manufacturer to get the factory part you need.” I don’t recommend Lennox to anyone! Lennox is a big pile of 💩💩 the 5 ton Lennox air conditioner I had was 15 years old it was time for her to hit the road!! 🤣🤣🤣 good job cleaning the coil John!! 👏🏼👏🏼👏🏼👏🏼

[@robincorprew9007]

Someone's power bill going down

[@Lazgar393]

The jet on your hose is too high and you could bend the fins. Also spray more at steep angle downwards from the top and the dirt just rolls off. You were just blasting it right back into the thing.

[@rruizproductions]

I just use water. Let it soak in for about 5-10 minutes, then rinse it. usually does the trick. No charge for that outside of a service charge.

[@billfarnsworth7700]

Good job Big John. I just cleaned out our outside condenser coil. It was covered with vines. I cleared out the vines, pulled the power, lifted the fan motor housing, and sprayed out the coil inside and out. I need to get some detergent. Then went down in the basement and changed out the filter. There was also an access panel to the indoor condenser coil, which was matted with cat hair in only one year. So I washed the indoor coil too. Last night it was 80 degrees inside the house. I had to shut off the a/c until this morning when I could get a look at the problem. I thought the condensing unit had gone back, but this morning I turned the a/c on, everything was running fine, even the squirrel cage. All the system needed was a good cleaning. Now I'm sitting here in a nice cool house while outside it's 90 degrees with high humanity. Take care John and thanks for posting these videos. Next year we're looking into getting another Goodman. This one has lasted 25yrs and still runs like a champ. We just figure it's time for an upgrade. I wanted to order one online, the entire hvac system with outside condensing unit and gas blower delivered to the front door for about $1500 then find a contractor to do the install. Trying to save a few bucks on a fixed income and budget. What do you think?

[@DouglasSantos-tt5ef]

hi i am from brazil, and i am too a technical conditioning air,here i wash inside to outside to,but congratulations to the work

[@TheJcrandazzo]

I hit my coil with a spray like that and my fins flatten down. They are so soft the spray pushes or bends them flat ?

[@MrRheo29]

I have no preference on how to wash the coils. Sometimes the crud does not want to come off from the inside out. So I do it from the outside. But, there are too many experts in HVAC ..... That don’t agree. To them I say to each their own.

[@jerrylockhart3069]

I’m sure that capacitor was dead or it’s going to be dead soon?. Good way to cause a refrigerant leak to the high-pressure surprised it didn’t leak also surprised him motor didn’t fail

[@erinkourelis7430]

I have a small room and this AC is very good in I Happy I purchased and will be using again next year.

[@alexsfit]

How much it’ll be a fair price I should charge my customers for a job like this??.. thanks

[@tundraboyblue]

It won't be long before that compressor goes, I've cleaned units like that and the compressor would only last a week or so afterwards

[@kennethlopez9677]

This is true. I asked an experienced HVAC technician about the best way to clean the coils. He said clean them the best way you can. It doesn't matter the direction, as long as you keep them clean and jet the water at a downward angle. Most home owners will not remove the fan assembly or take the panels off. So just rinse the coils with a water hose and a low pressure nozzle is better than nothing.

[@garyoconnordbaairrepair7775]

Getting my coil gun and what soap do you recommend for most coils?

[@archiesauls3672]

Air Repair Nu-Brite by Nu-Calagon is pretty effective.

[@payochannel1140]

This is the Lazy way to clean your AC coil without loosening screw. But 👇👇👇👇👇👇👇👇 I preferred clean from inside out. That is how we AC technicians do. Push the dirt dust from inside to outside,than follow by outside coil than inside,and from inside to outside again. That its...done and no dust left behind.

[@brendankaye7983]

bending heat sinks left and right. as a service tech i hate people that don’t take the time to spray directly at the coil or directly down parallel with the heat sinks.

[@tedrik1346]

Always from the inside out.

[@alexdemartine4758]

Excellent. Thank you for sharing your know how. Alot of people say that cleaning the condenser casues problems with the fins later on. I dont buy it. Plus the unit itself and the components have to work a hell of a lot harder if the coils are clogged up, which leads to problems with the components inside of the condenser later on.

[@yankeeownz9980]

I have a question, hopefully you can guide me in the ride direction. Info before question: I have an HVAC unit and the coil inside the house is set in an angel. I noticed last night rust is staring to build up on the pan that catches the water from the coils that leads to the drain pipe(s) and the bottom of the coil. What would you recommend I use to remove the rust that is on the pan and starting to come up the side of the coil? I do use the coil cleaner form twice a year and I know they remove dirt, debris, and other junk that gets in to the fins. I am stuck with Google searching how to remove the rust. I do not want to introduce no chemicals (acids, anodes, etc.) without hearing from experts in the HVAC field.

[@westonhuffman7908]

Well, Only if corrosive chemicals may cause refrigerant leaks.

[@الحمدلله-ح8غ3ش]

🌸سبحان الله وبحمده سبحان الله العظيم🌸

[@rhelouin]

I tried this on a Goodman package unit and that much pressure will bend ever coil fin flat and closed in a few seconds. I have never seen coil fins this thin. My suggestion is to check the resistance to bending of the fins long before spraying from either side as you can do much damage if the fins are a thin as they are on the Goodman unit.

[@reyrey2518]

Randy Helouin Goodman are the cheapest units you can get

[@mikedevo363]

When it's that dirty and neglected it really doesn't matter if it's pushed deeper in the coil. And it doesn't push it deeper into the coil. it pushes the debris out and into the unit. Which is completely fine

[@johnisraelhvac2019]

Thank you finally some one else gets it

[@jmcstore]

the truth is... it looks cleaner than before.. but you're only taking out what's visible. You have to hit it from the inside too.

[@johnisraelhvac2019]

Well that’s your opinion. And those are like A**holes everyone has one.

[@karbs76]

What was the temperature improvement after this ?

[@miguelquiroz1550]

I have done it ....depending how dirty the machine is. You can gain between 5 to 9 degrees on my experience.

[@rodneythornhill9526]

I wash them like that to and I have been known to wash them from the inside to make doubly sure it is clean. Even on Tranes I wash them that way instead of using a lazy flame and it works just fine.

[@edwardgarza5104]

What do y'all think is back there a brick wall 😂😂👍

[@xisotopex]

does this improve heating or cooling efficiancy?

[@RonniewbNC]

What is the purple funk-b-gone you are using?

[@analogaudiorules1724]

what kind of soap and soap dispenser do you use?

[@Tworth23]

Aren’t yuu suppose to clean coils from inside out?

[@earthling94]

Oh my GOD that was so satisfying

[@Geemoo]

I like how the narrative is peppered with anger

[@jamesfarmer2748]

I share your hatred for pump sprayers! They are all absolute junk designed for limited use and to end up in a landfill.

[@jg5488]

I just pee on it to clean the coil 😃

[@og6114]

Acid piss lol

[@rbilardo47]

John, do you have to use a toothpick to get out all of the stuff you packed into the coils? It didn't show that in the video. Just kidding, good job. I just cleaned mine yesterday, I have the Christmas garland type, worked out well. Love your videos, keep them coming.

[@kmreedN205]

Wrong! Rinse inside to out. Not at angles either

[@holeeshietpyro4072]

heres an idea... why dont ac manufacturers implement a hatch door on the top or easy flip top to stick your hand/arm/hose in and spray inside to out? situation like this i'd spray off the front first, then spray from inside to out, finish off with the soap wash.

[@JASMOOTH26]

You were supposed to rinse the coil cleaner off

[@delmarvaaireinc7742]

I use a top down approach in this situation, dont recommend spraying at angle on the coil. If you use proper technique you CAN clean outside in. You're not going to make money if you take apart all units...

[@j_scentv]

That’s not a complete cleaning, or deep clean.you have to go from inside to clean the coil :/

[@mattthomas1217]

I clean the same way I have been told by techs that you have to do in inside out, but either way it's still going to do the same thing.

[@bren70403]

Wow! That condenser is disgusting!

[@1Klooch]

Wow! If the condenser is sucking up that much crap, what's going on around it? I live in AZ, the Dust Bowl of the country, and mine is not even showing that much.

[@brandonhanley8912]

As long as the coil is doubled up it doesn't matter side clean it from. And from what I saw you have foaming nucalgon cleaner. If i can access the coil i wil clean it from both sides. Keep up the good work john. Ps. Love my coil gun too.

[@wdennis8]

Of course you will have those that find fault with what you are doing because they have nothing better to do. The only question is did you get paid for the work? If so, then why be concerned about foolishness.

[@DannyPlays96]

Win Dennis you should be concerned because when it gets stuck in the coil, in 6-7 months youll possibly have a burnout because of an improper cleaning

[@DreadhawkHussein]

This works but afterwards if u popped the top off you would see little chunks of wet shit stuck to the back of the coil which could build up over time

[@johnisraelhvac2019]

Lol no you wouldn’t

[@johnisraelhvac2019]

Lol no you wouldn’t

[@DreadhawkHussein]

Well we will agree to disagree I spent the last 3 days washing coils all day and I tried to be as quick and efficient and from my experience that's the result with a HEAVILY covered coil.

[@Heartgator]

You’ve got nothing to prove - everyone has an opinion - just show your way and move on brother - I do recommend that y’all ALSO clean and spray from the inside. This gives you a chance the clean-out leaves and the crud you blew in there.

[@Boojyman]

I clean coils this way everytime 👌

[@qeesher]

👍 Washing from outside is much cleaner and faster than from inside. There is no pressure to properly wash the coil by doing it from inside out. Even on tranes. If the debris is small enough to go inside it will just go through and that’s it. Never understood all the fuss about cleaning from outside/inside 😂

[@subhanpatel4355]

Why is everything a paragraph long?

[@robsp32]

Wouldn't it be better to vacuum the large debris off first and get that fur coat off before using the cleaner gun? Also have you considered a small electric power washer? I have a Ryobi thats about the size of a 15" laptop that does 1600psi.

[@arcticarrowhvacr]

I would use a whisk brush to get the heavy stuff off, rinse the condenser and then apply coil cleaner, wait 2-5 mins, and then rinse it off. Some cleaners have an acidic substance to them.

[@lilsavagegod]

@@arcticarrowhvacr the acidic can be useful to remove the dirt and hair etc... But bad Becuase it sometimes takes aluminium with it

[@truckinforever985]

Nice video John Coil gun is a must have

[@solarflare1008]

Wrong proceedings here but it appears that works.

[@eddierack]

What was wrong? I think he did a great job. You must be one of those inside to out people.

[@oldtimehomestead1554]

I always did it this way and never had a problem.

[@jb5796]

Does this clog up the inside of the unit since you’re spraying it into the inside?

[@eddierack]

There are drain holes on the inside

[@ba0700]

One risk by spraying from the outside of a dirty coil is clogging the drain holes on the inside.

[@anthonymorales6980]

Do i need to turn the breaker off the clean it

[@bg147]

Yes. If there is a shut off outside by the condenser, pull it. I have sprayed mine out while It was running but you want to shut off the current.

[@sycoticau]

Anyone that’s says this is wrong cleans coils the same way. I clean them everyday this way and if you have time to go from the inside out then you don’t have as many calls as most of us do in a day. Nice work

[@hvaccrystalaircon6775]

Good service

[@az9336]

The unit is installed on an area which is easily accessible. So why would anybody allow that much clog to accumulate. That's absolute nonsense of this person.

[@checolinseliz5385]

I don’t know what state is this but the whip it needs to be water proof, that’s a regular 1/2 flex conduit ...

[@oakandiron_]

Chip… on the shoulder?🤔

[@Spector_NS5_RD]

Whatever works, John. Is the unit back up and running? cooling?..........yes, you say? Great. I just love textbook geeks who service 2 units a week......"you're doing it wrong." I saw my first Sanyo Tri Zone mini split last week...... There were 3 tiny compressors inside the unit, one for each head, neat! Sadly, one of em has died :(

[@DanielHernandez-tp2tm]

I like this video. We got a lot of greens that think they know it all. Good shit brother. Love from Texas!

[@tarlvinrandall7009]

???To be fair yes, you do knock off a lot of debris but it's the pressure that aids in get the most dirt off the coils. If the pressure isn't good you will clog your condenser coil.