Bad AC noise

Matthew K

Matthew K

Line Up and Wait
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Sep 14, 2016
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Georgia
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Broke Engineer
I'm talking about an air conditioner. Not an aircraft :D. But really our 1st floor a/c compressor fan isn't running, and it's making a nice loud noise. The a/c unit is getting up their in age so the whole unit is probably gonna need replacement soon anyways. But I'm fairly sure its a bad capacitor, we've had the fan not spin before on other units its just never been this loud..Our a/c guy should be coming out tomorrow and I could just spend some time researching it but I really don't feel like it right now :D so I figured I'd see who would know just by the sound(and then possibly tell me I'm wrong) and maybe some suggestions on good air conditioner brands for the inevitable time when the unit has to be replaced.
Video:
 
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First, don't let it run more than 30 seconds without the fan because the system will over heat, the pressure will get too high and the compressor will stall, bad juju. Sounds like the compressor is running and the fan is not. Could be a contactor, capacitor or fan motor, not much else unless the compressor is smoked. Motor is most expensive, but I doubt that's it, the contactor or capacitor should be less than $100 each, probably much less, labor will probably croak ya. I would fix it, clean the coils and run it another 20 years.
 
is it a heat pump? are you running in heat mode?
 
Sounds like a run start capacitor. Most systems these days have dual run capacitors that gives both the compressor and the fan motor a good bump to get them purring. It there's not enough juice to get the compressor or fan motor going, they'll just sit there and hum. About a 15 minute job to replace. Might also want to check your relays and make sure they're not sticking or have burnt contacts.

Edit... if your system is making the same noise as in the video, then your fan motor is more than likely shot. Check your resistance. It could also be a bad capacitor not allowing enough juice to kick it on. Again... check your resistance and the capacitor ohms. I'd start with the easy stuff first. What you hear is the compressor motor. Don't run it too long or you'll burn it up.
 
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Yeah. Capacitor or motor. But usually the cap. They’ll tell you that you need a new AC unit. Don’t believe that story until you have at least three opinions.
 
Start it and manually spin the fan using a paint stirrer stick, yardstick or similar. It should then run. Assuming it does, turn t-stat down and keep it running awhile. Repeat as needed until repair man comes. Be careful with repairman though. Once had this happen and was told I needed a new compressor. New capacitor fixed it. Same unit was still purring when I sold the house three years later.


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it does sound like capacitor, very common. could be bad motor, also common. if it a heat pump it could be the defrost control board, as it supplies power to motor. either way it should be repairable with minimal cost compared to replacement. you could (not saying should) use something to spin the fan manually and see if it starts (make sure to spin correct direction).
 
Matthew K said:
I'm talking about an air conditioner. Not an aircraft :D. But really our 1st floor a/c compressor fan isn't running, and it's making a nice loud noise. The a/c unit is getting up their in age so the whole unit is probably gonna need replacement soon anyways. But I'm fairly sure its a bad capacitor, we've had the fan not spin before on other units its just never been this loud..Our a/c guy should be coming out tomorrow and I could just spend some time researching it but I really don't feel like it right now :D so I figured I'd see who would know just by the sound(and then possibly tell me I'm wrong) and maybe some suggestions on good air conditioner brands for the inevitable time when the unit has to be replaced.
Video:
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I had the fan blades fail (mechanically) in a unit about 5 years old. The motor was turning, but not the fan. I checked the cost of a replacement - and found it to
be more than expected - so looked around and found a fan on an old attic blower that, while slightly smaller in diameter, fit the shaft and worked fine.

Dave
 
denverpilot said:
Yeah. Capacitor or motor. But usually the cap. They’ll tell you that you need a new AC unit. Don’t believe that story until you have at least three opinions.
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That's why I do all my own A/C maintenance. Way too many shysters in that business. Nothing like screwing a customer over by charging $200 for a $15 cap change that takes them all of 10 minutes to do. Never mind the $100 per lb. freon charge when you can buy a whole 30 lb. jug for $100. ;)
 
Barneyfife said:
it does sound like capacitor, very common. could be bad motor, also common. if it a heat pump it could be the defrost control board, as it supplies power to motor. either way it should be repairable with minimal cost compared to replacement. you could (not saying should) use something to spin the fan manually and see if it starts (make sure to spin correct direction).
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I did try to spin it with the system off, to see if it was seized. I also tried to spin the 2nd, newer unit to see how hard it was to spin. Both spun, but the one giving issues did seem to have a bit more resistance to movement.
 
denverpilot said:
Yeah. Capacitor or motor. But usually the cap. They’ll tell you that you need a new AC unit. Don’t believe that story until you have at least three opinions.
Click to expand...

azblackbird said:
That's why I do all my own A/C maintenance. Way too many shysters in that business. Nothing like screwing a customer over by charging $200 for a $15 cap change that takes them all of 10 minutes to do. Never mind the $100 per lb. freon charge when you can buy a whole 30 lb. jug for $100. ;)
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Luckily we have a pretty good and trust-able a/c guy who mainly does the work to keep him busy (he's supposed to be retired). Any time we've had to use him before he always makes sure we know exactly what he fixed.
 
Matthew K said:
Luckily we have a pretty good and trust-able a/c guy who mainly does the work to keep him busy (he's supposed to be retired). Any time we've had to use him before he always makes sure we know exactly what he fixed.
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Fair enough. Turn it off at the outside cutoff if it’s making that noise, as someone else already mentioned.
 
you would need to spin while compressor is running as in your video, to see if cap is bad.

azblackbird said:
That's why I do all my own A/C maintenance. Way too many shysters in that business. Nothing like screwing a customer over by charging $200 for a $15 cap change that takes them all of 10 minutes to do. Never mind the $100 per lb. freon charge when you can buy a whole 30 lb. jug for $100.
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yes there are shysters, the cap even if it a dual should only at the 1.00 per mfd. so a 35/5 mfd would be 40.00 to you, my cost 15-20 dollars. but that's business. 100.00 a pound for freon, even r22 is high, but you will not buy a jug of r22 for 100.00. r22 should be around 45/lb to the customer.

and a good multi meter is great if you know what and where to check.
 
Barneyfife said:
yes there are shysters, the cap even if it a dual should only at the 1.00 per mfd. so a 35/5 mfd would be 40.00 to you, my cost 15-20 dollars. but that's business. 100.00 a pound for freon, even r22 is high, but you will not buy a jug of r22 for 100.00. r22 should be around 45/lb to the customer. and a good multi meter is great if you know what and where to check.
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I understand you guys need to make a living. But some of ya'll get a little too carried away sometimes. :D

I've got a small leak (2 lbs. a year) in my A-coil on my 2.5 ton unit and don't feel like pulling it out and brazing it, so I bought a jug of Dupont Suva 410A for $100 off of E-bay a couple years ago and have been topping it off each spring before the heat gets too bad. I also checked my 3 ton unit, and put a 1/2 lb. in it just to bring it back up to factory specs. I've definitely saved several $$$ by doing it all myself. ;)
 
i absolutely agree, some do get carried away, and usually wont be in business very long.
410a is cheap yes, around 100.00 a jug. 410a is around 15/lb. to the customer.
not everyone has the ability or equipment to do their own work. it good that you can. folks can buy a jug of 410a, have the gauges etc. but they need know how much to put in and what pressures should be, superheat, subcooling etc. although there are tolerances and its not rocket science, overcharge=bad/undercharge=bad!
i don't rip people off or take advantage of them. i don't advertise, all my work is word of mouth, i can't afford to rip people off. but i cant work to break even or for a minimum wage.
im always willing to help customer diagnose and let them repair is they are capable.

anywho. Matthew, its good you want to know and have knowledge of what going on. there are few different things it could be, all been mentioned already. could be easy repair for yourself or wait for the trusted ac guy.
 
I like to troubleshoot myself and then hire a pro who’s trustworthy like @Barneyfife to do the work and double check.

If I’m SURE it’s just a capacitor, I’ll swap it out. And even if it blows again it was only $15.

But I at least figure out what I think it must be before getting quotes, because there’s so many shysters out there. It’s just the easy way to tell if they’re lying to you up front.

I don’t mind paying someone to do good work. I just hate it when the bad ones walk in and tell you that you need a new system because a) there ripping everyone off, or b) they don’t know what they’re doing.

Similarly at work, we had an oddball but very efficient HVAC system for a small data center fail in summertime. The usual HVAC contractor said it was dead and to buy a VERY expensive new one.

Found out they were lying. The Japanese company that made the thing only keeps a handful of local contractors on their approved vendor list because the things are highly automated including troubleshooting and I’m sure those vendors pay to keep their latest tools on a laptop and training for staff.

Once we found the local approved vendor? 2 hour’s labor at a fairly high price (to pay for the diagnostic software no doubt) and $150 in parts.

We shared this back to our usual HVAC vendor and told them, “If you don’t know what you’re doing on our special HVAC units for the data center, just say so. Don’t lie to us. Giving us a quote to replace it left us wondering if we should shop HVAC providers.” Their local manager “got it” and told his crews to learn to say “no” to stuff they weren’t trained on.
 
Barneyfife said:
i don't advertise, all my work is word of mouth, i can't afford to rip people off.
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Too bad you're not in the Phoenix area. I'd have you come over and we'd get my leak taken care of. I don't have a vac and I just sold my nitrogen tank, so I need to find somebody that can handle that end of it for me. I had a guy that did all that stuff for me, but he moved away. He handled all the HVAC maintenance for our local school district.
 
if i was in your area i would definitely help you out. wishing i was in phoenix area right now instead of swmo

Matthew, lets us know what the verdict is.
 
Zeldman said:
Wow... that is a bad noise.

Has it been fixed..???
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When I shut off the whole unit for a while and started it back up the fan started spinning like normal, just somewhat sluggish at first and with the loud noise at first. AC guy says its the fan motor bearings going. He's got one on order for us.
 
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Update: Whole units being replaced :eek:, the fan worked for about another week, then instead of the fan completely dying, the compressor itself locks up, permanently. Oh well, the unit was going to need to be replaced soon anyways.
 
Matthew K said:
Update: Whole units being replaced :eek:, the fan worked for about another week, then instead of the fan completely dying, the compressor itself locks up, permanently. Oh well, the unit was going to need to be replaced soon anyways.
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Try restarting it after it cools.
 
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