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Discussion Starter · #1 ·
Hi... Have an older outside AC compressor that still works but has humming issues. I assume it's the motor. When started, it goes from a low hum to a high hum before going quiet for the rest of its cycle. Maybe an oil issue? I can get 3 in 1 oil to the motor's main shaft through some disassembly. There are no side plugs.

Not sure if it's worth it though? We're selling the property and I'm just trying to avoid a possible inspection issue. It blows cold air just fine inside.
Would the temporary humming cause an inspection concern anyway?

Thanks
 

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Sounds as if you're actively trying to hide what might be a problem from your potential buyer? Please go to a different forum for that type of advice.

I'm sure many of the professionals on this site know loads of "tricks" that they have had to repair for their own clients in the past. It would be very disappointing if they were to advise how to short change anyone.

Since you acknowledge there may be a problem the most I would advise is to be proactive and hire a licensed HVAC professional to go over the unit, effect any repairs and give the A/C a clean bill of health that you can proudly show the prospective buyers. That's how you avoid inspection issues.
 
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Discussion Starter · #3 ·
You have me completely wrong sir. I'm working extremely hard to give the buyer a well renovated home. It's been in our family for 45 years. The AC works. It blows cold air indoors. Like I stated, the outside compressor motor makes a humming sound for a few minutes and then quiets. I came here because I don't know if it's an issue? Maybe older units do this? Maybe I can fix it myself?... hence the DIY nature of this forum.

Don't be so quick to judge. You don't know me.
 

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You have me completely wrong sir. I'm working extremely hard to give the buyer a well renovated home. It's been in our family for 45 years. The AC works. It blows cold air indoors. Like I stated, the outside compressor motor makes a humming sound for a few minutes and then quiets. I came here because I don't know if it's an issue? Maybe older units do this? Maybe I can fix it myself?... hence the DIY nature of this forum.

Don't be so quick to judge. You don't know me.
My apologies if I misunderstood the comment; "trying to avoid a possible inspection issue." Sadly, that seemed to point in one direction, at least to me...

I still advise getting a qualified service man to look at it especially if you are working extremely hard to give the buyer a well renovated home - just seems that a professional would deliver the best documentable results.
 
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If it blows cold air just fine then I would not worry about it.

If the inspector mentions it and a potential buyer is concerned then let him have his own tech check it and you offer to pay for the checkup BUT be there when he checks it and see if he notices or documents the sound.

Don't ask and don't tell is my motto. Don't ask or tell the tech about the sound. There is a change in sound when it starts as it is building up a high discharge pressure and some units take 3-4 minutes before the freon pressures stabilize. Nothing wrong with that.

Post a video if it and maybe we can tell you what the sound is.

Turn it on right when the inspector arrives and maybe the sound will be gone by the time he looks at it. ( Ain't I clever ) :D
 

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To me it sounds normal. When the compressor starts it is unloaded and will hum loudly and as the pressure builds up it will quiet down. My fridge does the same thing.
 

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Two years ago we sold our home and replaced our 30 year old HVAC system and hot water heater to make the home more attractive to a potential buyer. But now its a sellers market so I would not touch your AC since it works unless the home inspector brings up an issue.
 

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Anyway, the market is so hot right now that even if an inspector flags it, a buyer is likely to accept it anyway. So many homes are basically being sold "as-is" now—the inspection is more of a function of "what work are we gonna have to do soon" and less of "what work does the seller need to do before we buy."
 

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Most home inspectors know squat ( nothing ) about furnaces and ACs other then does it run and is not leaking water or looks like it is burnt or black ( furnaces ) so I would not worry about them.

They look for bad shingles and water stains and obvious problems but few know what a AC should really sound like.
 

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there is a product that I have used on OLDER well run ac systems. It is called AC/renew.https://www.nucalgon.com/products/total-system-protection/ac-re-new/
It is synthetic oil and will help noises and lower amp draw. At least it did for me the two times I have used it.( my units) Checked before and after with amprobe and decibel meter.
I ran into this when the Nucalgon sales man stopped by work and offered up some samples, problem was it took us a long time to find a unit small enough for the samples. Our machines were 2000 ton and above. We spent a million a month with Nucalgon for water treatment for the cooling towers. They were not going to upset a good customer over a product that does not work.

Last bottle I got was $60 bucks, and you need the device to inject it into the system. You .may find that you can not buy it has to be a licensed contractor in some places. This product MUST BE MATCHED to the freon in the system. I can not stress this enough.
This will only work on the compressor, not a cooling fan.

I do not believe in snake oil or easy fixes. This product has worked for me in the past. I have no idea if it will work for you.
 

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Discussion Starter · #11 ·
Well thanks everyone for your suggestions. I decided to call a local HVAC company to come out. He's a contractor I know from work and has a stellar rep. He'll come out and maintenance it for $80, including coil cleaning, lubrication, Freon and filter. He'll check the attic furnace too. The motor in this compressor is at least 44 years old! I'd like to give it a fighting chance before the new owners have to replace it.

Thanks again
 

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44 years old. It doesn't need a fighting chance. Its had a good long life span. Expect potential buyers to ask for an allowance for replacing it. Doesn't matter how quiet it is, or isn't.
 

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At 44 yrs old it deserves a Parade and marching band and retirement party. :love:

Must be one of those ole GE Weathertrons or Tranes.
 

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If it passes a check up, get a receipt saying that and use it to minimize what the buyers want to accept an old unit. If it fails, get a price for a new one and you have information to negotiate with. I wouldn’t replace it unless there is a great offer that will go away without a new unit. I would rather concede the cost of a new unit than go through replacement, if possible.
 
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