Common Air Conditioner Capacitor Failure Symptoms

Capacitor Failure Symptoms are sometime harder to identify without the right tools and expertise. Capacitors can be found in several different sizes and shapes. There may be one or multiple capacitors included in your ac with regards to the design. While the most popular capacitors are the types found on circuit boards, the ones most associated with air conditioning will be the bigger capacitors that assist start and run your motors. There are several motors present in an conditioner and heater systems:

  1. Compressor Motor Run Capacitor: Here is the most popular capacitor that fails. Most of the time these are duel capacitors, which means that there are 2 capacitors built into one. A duel capacitor will have three terminals on the top where a single capacitor will simply have two terminals on top.
  2. Outside Fan Motor Run Capacitor: That is the smaller capacitor found with or part of the Compressor Motor Capacitor. It helps start and run the outside fan that blows air through the outside coils.
  3. Indoor Blower Motor Run Capacitor: Similar to the outdoor fan motor capacitor, it is a small, single (two terminals) capacitor that will help start and run the indoor blower motor.
  4. Start Capacitor: Some models include an auxiliary start capacitor that helps jump start the motors. Most are found on the compressor. These are less common.

Why do capacitors go bad

When capacitors go south, they either go out entirely or they decline in strength. The decline is measured in the “capacitance” units called micro farads. When the capacitors are produced, they are labeled with their specifications capacitance and a range +/- from the design capacitance. This range is the allowable operating range, usually labeled in a percentage range, for the capacitor. If the capacitor starts to fail, the capacitance measured will be outside of the labeled range. Sometimes these are difficult to find any symptoms unless you have the proper tools. Warning, there is a risk of severe shock, so do not try this at home.

Diagnosing a bad capacitor

If a capacitor goes out completely, or is severely out of its operating range, it may prevent the motor affiliated with it from running completely. If the compressor motor is not working, then the air conditioner will not cool. If the outside fan is not working the compressor may cause problems and will short cycle or cease working. If the indoor fan stops, you’ll find that there is no air blowing through the vents.

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809 thoughts on “Common Air Conditioner Capacitor Failure Symptoms”

  1. My LG neoplasma split will only run for about 10 seconds before the outdoor unit stops working. The indoor unit continues working but the fan icon on the electronic display disappears and the outdoor unit stops working. after about 1 minute, the fan icon on the indoor unit comes on and the outdoor unit runs again for about 10 seconds before shutting off. this is repeated over and over again. There is no cooling effect and no water coming out of the drainage pipe. When I disconnect the powerline to the outdoor system, the indoor unit tends to work properly with the fan icon on and the fan blowing for as longs as the system is on. Hope that I don’t have a big problem on my hands?

    1. It sounds like you have a serious problem but the information is not enough to provide you with any kind of valid diagnosis. You had better call a professional to put some test equipment on the unit to find the problem.

  2. I have an old carrier heatpump with a Positive Temperature Coefficient Resistor start circuit (like made with a ceramic case) that was replaced with a supco super boost spp6 ptc years ago. Now it is hard to start the compressor again. Should I replace this hard start capacitor with a 3 wire version (ie 521) or would the torque be too much for an old heat pump (over 35 years old)?

  3. have a walk-in cooler that needs to be about 35F. The compressor everything seems to be ok until unit runs for about 30 minutes. the amps get a little high(rla is 10.6, unit slowly as txv opens/closes, increases up to about 14/15amps) then all of a sudden it acts like it is trying to stat all over again and the amps spike up to 40+.(trips breaker) Let it cool some and the time lessens but same issue. Could it be the run capacitor. I checked it originally and it was 20.1 for a 20 microfarad part. I changed the start capacitor as it was reading way high(145-174, reading mid 190’s). The box is starting out warm at 70/72F. Can a run capacitor appear fine but fail under load causing this issue? My mind says yes. Thanks!

  4. Hello,

    My ac stopped working last night, I opened the furnace and hand spun the blower fan and pressed the safety switch and it runs fine, if it’s not kick-started it just hums, would this be the capacitor for the blower fan causing this?

    1. Sounds like the capacitor. I would also want to watch for the motor failing since you are resetting a high temperature switch.

  5. I have an AC unit that the fan could be jump started so I replaced the capacitor. It worked great for five days and then the same problem. What will cause new capacitors to go bad?

  6. Hello, In July my ac had a problem. The repair guy came and said it was a bad capacitor. It did look burned. ..He replaced it. IT worked fine for a little over a month, then for about a week, the inside fan seemed to struggle and not turn on. Finally stopped working. Called the Ac guy out again, and said that the entire motor was broken. …When he took it out, the capicator was very burned looking too, and seemed much smaller than the original….my question is, do you think he put in the wrong size capacitor, and that is what broke the motor?

    1. No, its a different capacitor. You have 3 capacitors in the system. The blower has it’s own and yes both the motor and capacitor can be gone. Having an annual maintenance on your unit may have prevented you from burning out your motor.

  7. I have an issue with A/C not cooling very well. It is with 1 year old condensor with 5 year old evac coil using r22. Per two different hvac contractors, freon level is normal but subcool is bit high. Temp difference maintains 16-19. It coos down at night but it will not cool with temp rising outside. AC stops before reaching the temo and run again and again until it reaches the temp at night.

    I also had an issue with gas furnance that shut off continously even after temp sensor was replaced. I had to shut off gas valve a little to run

    For both AC and furance, the unit runs better with stopping if I let it run with evac coil cover opened up a little.

    I am curious if my blower motor is not blowing enough air or capacitor is bad. I ordered air flow meter to check myself next week or some.

    Is there any way I can check the blower and capacitor myself if that could be the reason?. Is there something else that should be checked?

    Coil was cleaned up and filter is clean and I use cheap kind tp have more air. This started after I got the condensor replaced last year. The original installer replaced the piston and tried different thing and gave up.

    I am afraid to call another hvac just to hear sales speech. Both hvac just suggested to replace the system.

    1. Why would anyone put R22 system in right now. We are converting all our customers over to R410A. You have major issues in that it sounds like the units are mis-matched. That is a problem. It will never run correctly if that is the case. Do you know if your blower is set to the right CFM for your ducts? Probably not so measuring air flow is only going to give you half the story. Sounds like you’ve gotten yourself in over your head. My only suggestion for your problem is to get a HVAC specialist to review your system, load, and sizing. There are no short cuts.

      1. It was matched to the existing setup as 4 ton coil and coil was R22. I am not sure what makes you say it us mismatched and I am curious. From what I see the blower is set up as medium/high for AC, medium/slow for heating.

        I called two different contractors already and they did not have a clue. Well, I can try one more but wanted to have some idea.

        One mentioned there is restriction in the air by looking subcool but did not bother to look further.

        I was curious if that could be blower or capacitor going bad or even heat exchanger(no co2 per my sensor though) or something


      2. It was matched to the existing 4ton coil when the condensor was replaced. Why would you think it is mismatched? I am curious what makes you think that.

        The blower is set up for high even though I am curious it is functioning correctly.

        Two contractors came by already and they both did not have any clue what is causing this issue.What do you think I should ask third contractor to check to find out the issue?

        I never had this issue with the same size of unit and duct before…..thanks for reply

      3. I mean matched as designed to work together. Just because it is 4.0 ton on each does not mean they are matched. I cannot put a Trane coil and a Rheem outdoor unit together they are not designed to work together. Yes you can have air restrictions going on, duct design/layout problems, refrigerant restrictions, leaks, contamination, non condensables, motor bearing issues and much more. The information you have provided just tells me you are in a mess way over your skill set. Better get a professional.

      4. The builder used two different brands before the replacement anyway. I did not think musmatch would be any issue. Pressure and delta t is normal. Also I am not sure why I would have this problem with ac and furance together just because the condensor was replaced. I guess it could have been the coincidal but furnance get too hot with code 33 and a/c not cooling with the proper delta T made me think it was some kind of air flow issue. Since the evac coil/filter are clean, I was guessing it could be the motor/capacitor which led me to this site. I will try another contractor to see what they find to fix. Thanks for the reply

      5. It can be. Mismatch can void a warranty due to engineering differences. Some inspections departments wont allow mismatch parts. And to clarify mismatch, different furnace and AC are not considered mismatch. Mismatch refers to a different brand for the coil and outside unit.

  8. My ac was working just fine then all of the sudden I heard a semi loud noise from outside, and the fan and compressor both do not work. I took the capacitor out, and the terminals were kind of rusty. The capacitor looks kind of old. I tried to drain the capacitor terminals, but it doesn’t seem that there was any charge in the capacitor. Just wondering if I am correct that it is the capacitor or do I need to get help? I haven’t put a new capacitor on yet.

    1. Get help. A loud noise is either the refrigerant blew a hole in the system or an electrical short. Either way you have serious problems. Capacitors are not measured by checking the charge, rather checking the capacitance.

  9. If a capacitor is going bad can it cause a thermostat to stop sending a signal to turn the condenser unit on? I woke up to the attic unit running by the outside unit not on. This happened in April too and Nest told me the thermostat was bad. They sent a new one out and then the exact same thing happened yesterday. Replaced the thermo with a Honeywell and it was fine as far as turning on. 4am this morning fan is making a racket so I went outside to look. Forgot to turn unit on so I could stick test the fan outside and when I went back in and turned it on the thing worked fine. I’m thinking capacitor going out but would that cause thermo to do that? Going to replace the capacitor today just in case because it’s 3 years old and tech said Grainger ones aren’t that good.

    1. A bad capacitor has no affect on the operation of the thermostat. It is on a completely different electrical circuit. The thermostat just turns on the switch to the condenser. The condenser runs on high voltage when this switch is closed. The purpose of an AC motor capacitor is to provide a second phase on what is otherwise a single phase system. Motors prefer 2 or three phases to help them run smoother. A bad capacitor means the second phase isnt being generated and the motor is attempting to run on only one phase. This puts undue stress on the motor magnets and bearings which can lead to early motor failure. But in most cases a bad capacitor or a bad motor will not make a “racket”. However, that being said, if the fan has already damaged the bearings, they can squeal or be so bad that the fan blade is off center which can rub other parts making a “racket”. Good luck.

  10. Thanks for any help at all. I have one of those heat pump units (Climatemaster Tranquility TRC floor-standing console) like in old hotels. No thermostat, simple on/off switch.

    The fan works perfectly fine but the compressor turns on maybe 30% of the time. I hear it try to turn on and fail. Or it would run for 5 min and stop. Sometimes it won’t even start. When it does run, the air is very cold so I don’t think the compressor itself is at fault.

    Do you think this would be a blown capacitor? My AC tech came by and guessed that this was it. I have an entire new unit sitting around ready to be installed but I’d rather spend $10 on a capacitor than $2350 + $800 installation on a new unit.


  12. Hi there!
    We have a rental house (already left a message for my landlord but came across your site) and the ac quit working AGAIN. About a month ago the insixe quit blowing air, fan wouldn’t even come on. Outside fan worked fine. HVAC came out and I believe he replace a control board inside. Yet again the same thing happened today, outdoor fan works but inside no air coming through the vents. I don’t see ice anywhere, honestly I’m not sure if im really looking in the right places. Set the thermostat to fan and off like before and no air. The copper pipe coming out of the unit is cool and the pipe next to it black insulation stuff wrapped around it) is cool also but very damp. I pulled the cover off to look for ice, didn’t see anything. It makes a slight hum with the safety switch? (Little nob that pushes in when the door goes back on) engaged but doesn’t try to quick on. I apologize if my lingo/terms arent correct. I don’t know much about ACs. Any thoughts? Seems odd to me that they board would be bad again this soon but it’s the same issue all over again!

  13. We are having difficulty figuring out what is wrong with our Trane air conditioner. I have a licensed HVAC specialist coming to look at it again tomorrow but he doesn’t have any ideas yet. It is the 3rd time it has broke in 2 months. Last week, the unit would come on and shut off within 5 seconds and kept doing this over and over. I shut it off immediately since I was worried it would damage the system. He came and found the second leak, fixed it, and we thought all was well. It started doing it again two days ago. I shut the unit off, he came roughly 2 hours later, ran some tests and the unit ran fine for him. It acted fine yesterday but today it is doing it again. Instead now, it will try to come on 3 or 4 times and then eventually power up. It would repeat this cycle every 8 minutes. We shut it off and let it cool for a hour and it is now running fine again. Any ideas what this could be?

    1. These are the kind of problems that will require putting test equipment to the unit in several different places to get readings. From the readings, the technicain can begin making assumptions on performance of the parts. Things to check are static air pressure, refrigerant pressures, pipe temperatures, motor temperatures, amp draw of the motors, voltage and resistance across the controls, etc. It may take some time.

  14. Hello, I’m in Texas – it gets hot in afternoon (~ 100+). My AC is out of warranty. It can’t keep up in the afternoon – however, I do see that it blows cold air when I turn the AC ON vs. the “fan mode”. it cools upto 84 degrees, and can’t cool further in the afternoon. In the evening, when the temperature is not as bad – it is able to cool pretty good.

    I had a contractor come in an put R410A – didn’t help for even a bit. Then, the contractor said that the AC unit outside needs to be replaced because he thought that there is a leak in the outside unit. There is nothing wrong in the inside furnace, but said that I should probably look at replacing that too since its 10 years old.

    Then I had another guy come in – he hooked up his tools on the AC unit to check the temperatures, and diagnosed the issue saying that the coil needs to be replaced.

    I’m confused — should i replace the coil or the outside unit? any thoughts on what’s going on here? thanks in advance.

    1. Sounds like the second guy is guessing. You need a leak search performed to determine where the leak is and replace that part. As far as replacing the 10 year old furnace, there are many companies out there who will say that for any unit over 10 years old. However, some furnaces have 20 year warranty on the heat exchanger which is the #1 cause for replacing a furnace. Most will last at least 15 years. Even outside furnaces typically last 15 years in the worst conditions. Unless you have an outdoor furnace and live at the beach, 10 years is a little soon. But to caveat that, it can happen but a full inspection of the heat exchanger should be performed to validate the need to replace it.

  15. When I turn on AC and set at any temperature below 80, AC cools down at the first time. However, if the inside temperature reaches 80 degrees, outdoor fan continuously repeats short-running and stopping. And it just keeps 80 degree what temperature I set. I changed the thermostat and also checked that refrigerant is OK. So it should have other problems.

    1. Yes you definitely have other problems. There are several that come to mind. You could have bad bearings on the fan motor causing it to over heat. You could have a short in the control or power wires to the fan, you could have a bad defrost board, you could have a bad fan relay. You need a good voltage meter and a strong diagnostic ability to determine the electrical failure for the fan.

  16. I had a new/packed 1.5 ton split unit,purchased 8 years back.Today installed, woked fine for few hours, then left running and when i came back, it was off. When tried to turn it on,n saw at ampere meter, it hit to 56 amps n light started flickering.Turned off again n tried couple of times after some time but with same result.So now off.
    Is it bad capacitor which is preventing compressor start n drawing huge current or what.? Plz advise

  17. I have 3 wires going from what looks like a breaker on the side on my house going to the board on the unit it’s self that has t1 t2 on one side and l1 l2 on the other side the problem I’m having is the red wire coming from the breaker outside of the house going to the board melted I replaced it and 3 days later it melted again replaced it for the third time and same thing 3 days later it melted and help please

    1. You are pulling too many amps for the wire to hold. Either the wire size is too small or the unit is pulling too many amps.

  18. Hey,

    Thank you for sharing your wisdom with those of us who have no idea what we’re doing.

    For the past week I would hear the AC unit outside commit a few false starts (best description would be revving the accelerator on a car), yet the unit would still work. Yesterday, the AC would not turn on. I turned off the unit and turned it back on. Setting the temp a few degrees below room temperature, I heard the “click” and the fan came on (but not cold air). I noticed smoke coming out of the AC unit. I turned it back off and went outside to inspect. It smelled like burnt plastic and I am now awaiting someone to take a look.

    Please let me know what you think it is, and how much the estimated cost would be.

    Thank you again

  19. Sorry to repost. I think this is the correct discussion.

    Two year old carrier ac/furnace system. I added a Safe-T-Switch to secondary condensate outlet this weekend. I tested switch by holding upside down and after 90 seconds (or so) system went off. I put switch back in place (system comes back on), leave attic and then notice no cold air. I also notice very load compressor outside, which eventually shuts off (with fan continuing). I thought something was fried, so I turned off breakers and left system off about 30 mins. When I turned back on…back to normal…usual quiet compressor with normal cold air. What was likely cause of temporary LOUD compressor and no cold air? Read somewhere that can happen when turning system off and on quickly and is due to “head pressure”.

    1. Thanks for the reply. Are you referring to fixed orifice pistons (as opposed to some kind of motor piston)? System seems to be functioning fine since that one event. I’m thinking I’m due for regular checkup service call. Is checking pressure and amp draw typically included in such service?

  20. thehvacguy, my outside unit fan runs but the condenser motor does not. The air handler motor runs too. What are the chances that the cap for the condenser is bad?

  21. I have a rental and ac fan works fine and air is blowing out vents. Just not cold air. Hvac guy said it was a bad capacitor. Approx fix $1000.
    Any thoughts. Just not sold it’s a bad capacitor.

  22. Hello, I have a Rheem system with heat pump & central air. Sometime in the early morning the inside unit shorted out the themostat. We thought it had just went bad & replaced it. As soon as we turned the breakers on the inside unit back on it shorted the new themostat out as well. What would be causing this? We called the installer but the can not come out for a few days & I have asthma problems. Or system is only 6 years old.

    1. You need someone to come out to find the problem. It will take someone with a multi-meter to determine the root cause.

  23. Have a two year old AC unit, now and then the compressor outside starts making a much louder noise, when it does this the air coming from the compressor is cold and the air from the registers in the house are not cold just ambient temp. If I leave it doing this after about 30mins the compressor shuts off complete (I assume maybe overheated) the fan keeps running and the system acts like it’s working normal so I shut of the stat. After about 1.5 hours the compressor will function again. If the compressor makes the louder noise and stops pushing cold air in the house if I power cycle the system straight away before it cuts out it starts up normal. It’s random. Could this be a capacitor going? Sometimes when its working the air from the registers is nice and chilled works great and massive amount of hot air from the outside fan from the compressor and the compressor its self is very quiet. But sometime the compressor is a little louder than normal and the air is not as cold but does chill the house down. Then on the extreme very loud compressor and then cuts out. Any ideas, I’m hoping a cap?

      1. Had an AC person look they can’t find a fault and say its OK. but it still cuts out now and then. Its doing a new thing now, I hear the compressor stop for about 1-2 seconds then I hear the clonk noise the compressor makes when it start up. And this is random it’s like its restarting mid cycle. I have not managed to time it right yet that Im next to the compressor so I’m unsure if the fan stops spinning or not. But the compressor does, its not the stat in the house that just thinks everything is normal.

      2. Sometimes the problems are intermittent. It is very difficult to diagnose what is wrong when it is operating correctly. Sometimes you just need to wait until it fails again then do not touch it and quickly call a technician so they can see the failure.

      3. We changed the cap still no joy, but I actually have fixed it. I had a Nest installed last year and this is the first cooling run for it, it turns out the power stealing feature was cause it to restart the compressor. I run a C wire Saturday and as of today still working no restarts or cutouts. Thought I would share incase anyone else has this issue.

  24. I have a question about my Bryant Heat Pump. A month ago I noticed low airflow from my vents. I checked my filters and they were clean except there was a piece of ice on one of the prefilters. I opened the cabinet in my basement and the evaporator coil was entirely encased in ice. I melted it off and it went back to normal. It would freeze like that every couple of days until finally the unit stopped working. I called an HVAC tech and he said the capacitor was bad and replaced it. He checked the refrigerant and said it was fine. The AC started to work again. He said the freezing came from too much humidity in my basement. I had a dehumidifier in there but I bought a second one to add to the first. It should be noted that the unit is a 2010 date of manufacture and I’ve had this house since 2012 with no freezing prior to this so I’m not really buying the humidity suggestion.

    Here it is a month later and it froze up on me again 5 days ago and now the AC is not working much like it did the first time. The fan will run but as soon as the compressor turns on the air flow from the vents completely dies and there is no cool air. Has my capacitor gone bad again and what could be causing this?

    1. He is totally wrong about humidity. The coil will freeze for only 1 of two issues, not enough refrigerant or not enough air flow. Sounds like the refrigerant level is AOK so lets consider air flow. You found a bad capacitor. Did you know the fan motor can go bad if you run it for extended period of time on a bad capacitor. Sounds like your fan motor is now bad. You didnt mention filters so make sure those are clean.

  25. HI. 4 Ton York that is 8 yrs old is acting up. The fan and compressor shut off together intermittently. When i pull the disconnect and re-install, it kicks on. then 5-10 mins, it shuts off again. No tripped breakers, no loose wires that i can see. Capacitor is OK, changed it anyway and still does it. Did it in 110* heat and again today in 80* heat with low double digit humidity. Had gauges on it and everything looked great. Even rinsing down the condenser didn’t help. When the unit shuts down, I tried to “stick” start the fan and it doesn’t get power until i pull and re-install the disconnect. There is a buzzing sound from the compressor when it is running. So i think its electrical, but can’t figure it out…any other ideas i should check?

    thanks in advance.

    1. Could be a bad low pressure switch. Check the voltage across the capacitor coil when it shuts off. If zero, then some control or short is causing it. Find what is making the voltage drop and you have at least the problem area.

  26. My capacitor failed overnight and I got it replaced this morning. However, now, I’m unable to reach the temperature set on the thermostat by a few degrees. What could be the problem?

    1. More than a dozen different reasons. You need to measure things like voltage, pressure, static pressure, resistance, continuity, and much more.

  27. Recently my the condenser unit has been making banging sounds when it starts for the first time each day, after a few seconds it settles down to it’s normal rattle noise. BTW the condenser unit was replaced 2007? and has always been noisy and rattles. Subsequent starts are smoother and less noisy.

    I know internet trouble shooting is a long shot but I believe the sound comes from the fan is there anyway to isolate the issue and make sure it is not the compressor?

    The inside handler/furnace is original to house 1994 so I know I am running the obsolete R-22 and facing an expensive replacement sometime in the future.

    Thanks for your time.


    1. Probably loose or rusted screws and connections. Could be the fan is unbalanced. Could be several other issues. I would need to hear and see it.

  28. My outdoor fan intermittently stops working. Turning the system off and on again will get it running again, but then it eventually stops again. capacitor issue?

    1. It could be. But it could be several other issues. All of which involve electrical troubleshooting. Better get some help.

  29. Hi hvacguy,

    I’m having a problem with my AC. It cools in the bedrooms, which aren’t large, but it doesn’t cool very well in the living room which is much larger. I can hear the compressor and fan outside come on, but they seem to be running slower than normal. I’ve felt the lines at the service valves, and one is cold, but I assumed the high pressure line would be very hot to the touch and it wasn’t. Im about to disassemble the duct to the living room to check for obstruction, but I was wondering if there could be a cause to the compressor seemingly running weak and the biggest room in my home not cooling. Any help would be great.

    1. It depends on where the thermostat is mounted. If it is in the cooler room, then the unit is functioning normally. If in the hot room, then it may need calibrating. As far as the different room temperatures go, that is a duct design issue. Proper duct size and layout is critical to proper room to room temperature difference.

  30. Fan motor went bad on outside unit purchased same motor installed it runs fine but no cold air and system is fully charged any ideas

  31. Got a question – My ac unit fan works fine; but when the compressor tries to fire up the capacitor draws power from the line and my lights dim for about 2 seconds then repeats every 3 or 4 minutes. It is not engaging the compressor. A few days ago it was working flawlessly. When I shut the unit off I can hear the capacitor buzzing back at my indoor circuit breaker. Have any ideas? Does that sound like a bad cap?

    1. Its not your capacitor but your contactor buzzing. Could be severely pitted which can prevent the compressor from starting.

      1. Thank you for the information; and that is a good call on the pits on the breaker/rack. I had already ordered a new capacitor just in case – because of all the various problems and symptoms noted abroad the internet. Might want to also consider my symptoms as a capacitor fail because when I replaced it – the AC started working again. From what I could tell before replacing the cap – when all power was removed the capacitor was vibrating and humming also in the outside unit. While I know that capacitors do hum some while in use; this thing continued to hum and it just reminded me of bad wiring discharging. Thanks again for the reply!

      2. I observed a strange problem with my AC. The compressor kicks in for about 1 second, every 3 minutes consistently. When it starts it makes a little buzzing noise Blower works very well but there’s no cooling.
        Any idea what can be wrong.

      3. Check the contactor for pitting or burned ants. If thats not it, you need a technician to look at pressures. My next assumption is you are low on refrigerant and the pressure switch is shutting it down.

  32. Our outside unit stopped working yesterday. When turned on it clicks and can hear soft humming and fan doesn’t start. I can get fan start manually but the unit never kicks on.

  33. Last summer my blower motor had a hard time getting going and would then spin very slowly. I switched out the capacitor for new one and it fixed the problem.

    Tonight when I came home from work I noticed a burning plastic smell and the blower fan is moving rather slowly.

    I am wondering if it could be my capacitor starting to go bad? If a capacitor is starting to go bad would a symptom be a slower-moving fan?

      1. After further inspection of the capacitor, i found that the capacitor terminals were corroded, loose at the base and the rubber boot cover had melted some causing the smell. After changing the capacitor and the scortched connectors, the fan began running normally.

        I was surprised to see the capacitor terminals so badly fried and loose to the point the ceramic buffers crumbled of as I disconnected the wire connections.

        Seems as if all is well now that the capacitor has been replaced.

  34. Hi Hvacguy,

    Our AC started blowing hot air on the inside of the house and cold outside. We noticed that The prong on the terminal for the compressor on the capacitor appears burnt. We moved the wire another prong on the same terminal and it fell of on its own after a few minutes but the air was cool inside during the short period that it was on. Do you think that replacing the capacitor may fix the problem all together? Also our capacitor has 4 prongs on all terminals does that mean something?

    1. Each terminal on the capacitor is marked with F C and HERM. Proper placement of the wires is crucial. How many prongs on each terminal is not important. But some manufacturers use 4 on Common (C), 3 on Herm (H) and 2 or 1 on Fan (F) but some have 4 on all three. Crimp the wire connector so that it is tighter when you apply it so that it is assured to stay on. Replacing the capacitor is only necessary when it is operating outside the specified rating limits.

  35. 98 degree day the Ac was running for hours non stop heard a squealing noise and went out back and the fan in the unit was not spinning.

    Turned off the Ac checked that the fan spun easily turned the Ac back on and pushed the fan it worked for about 10 minutes than the fan quit. Tried that 3 or 4 more times to the same results than just turned off Ac to prevent more damage.

    Is this simply a fan capacitator or do I have bigger issues?

    1. Start with the capacitor. But note that running for a long time on a weak or dead capacitor can damage the compressor and fan motors.

  36. I installed new cond fan motor with five wires old fan had three installed red and black to contacts brown to capacitor did not use purple and yellow started unit it ran proper direction then made a sound so I cut off unit and restarted unit ran opposite direction I changed direction with leads provide started unit up it ran for while then overheated and now will not run comp still runs do you have any ideals did not change capacitor

  37. My AC capacitor blew off and all the wires are melted (looks like there was a small fire). The unit is still under warranty (was installed in 2006) and the company is proposing to replace the capacitor and the wires to fix the issue. Should I accept their proposal or ask for a new unit ? I’m worried that the motor (or something else) will fail soon and that it won’t be under warranty anymore.

  38. Posting this out of frustration. I live in Miamk, FL and its hot as hell lately here, record heat. Inside my house too. Spent $250 replacing capacitors and other electricals on AC with a tech, and another $250 cleaning the coil inside the house, same tech. Initially I noticed coil would leak on top filter after unit reached desired temperature. This was the initial claim that started this. Fixed electricals cleaned coil, several days later I noticed a drop leaking on the filter again while I was just taking a look at the coil out of curiosity. Told the tech about this and he came to check and tells me a drop every couple of.mins on the filter is normal since the air getting sucked in will dry it. This sounds stupid to me and I’m looking for another tech for a second opinion. My house takes like 5 hours to go from 79 to 75 and before dropping $500 on this tech, the unit seemed to work better when it was dirty and the electricals were not swapped yet.

    1. I feel your pain. Unfortuately there is not a lot to go on here. He may have found issues with those parts. He should have checked to make sure the unit was working properly after the parts were replaced.

  39. Replaced the capacitor for the blower motor this morning because the system was buzzing but not starting the motor (which spins freely by itself when turned by hand). It worked for half a day and then I’m back to buzzing at the blower for about 60 seconds every 5 minutes or so and then nothing. And to make matters more frustrating, it randomly kicked on just fine at one point. Checked the circuit board and all the connections look fine (no blown solder points). Any thoughts?

    1. Sounds like a PSC motor with a capacitor. In that case I would be checking the fan switch or fan control board. Then also check the fan motor. Any one of those could be the root cause.

  40. Just replaced our contactor, and the start compositor as well as the transformer on a 5 ton split unit by carrier. Notices that my house is not cooling as before these parts was replaced. Some suggestions is that the compositor could be bad. Everything runs but the air is not as cold coming inside the house. The compressor and panel is cold on outside unit. The thermostat dose not go below 80 in the day time. It takes it a while to cool to 73 at night.

  41. my air conditioner will go all day cool air , then about 5 at night it will stop and hum sometimes i kick it and it will go seems just at night it stops and hums , told it was not capacitor what do you think thanks

    1. Could be a capacitor, could be a short. There are several things that would need to be eliminated as possibilities. You probably should seek a professional to check out the unit.

  42. I noticed a vibration/humming sound this afternoon and I recorded it. It would vary in intensity and at times would go away. About 30 minutes later the lights flickered and the ac was no longer cooling. I went outside and found the fan not turning on the unit. Help?

    1. Sounds like some severe electrical issues that should not be done without some serious training. Better call a professional.

  43. Our indoor AC unit was working just fine until 2 days ago it started making a squealing sound off and on while running. Woke up this morning to the unit not working at all. Could this be the blower capacitor or something else?

      1. My ac went out last night this morning i look at it and saw the fan trying to start i used a stick and to help fan to start it fan ran but notice no cold air coming

  44. Hello.. Need help determining
    My air conditioner problem.
    1. Outside fan continues to run even though the thermostat is turned off …. Tried to replace the thermostat and it did not help.
    2. Would charging the unit help? We believe it is low on freon because it also continues to freeze up on us.

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