Central AC unit hissing sound!!


  #1  
Old 08-05-10, 01:22 PM
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Central AC unit hissing sound!!

Hello i am trying to get some info concerning my AC that has not been cooling enough.. I thoroughly cleaned the unit and i oiled the fan.. I checked the evaporator and it was clean.. This morning when i turned it on i heard a loud hissing then the fan suddenly stopped so i flipped the breaker so the compressor wouldnt overheat... Any help will be appreciated....Thanks for any help
 
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Old 08-05-10, 02:06 PM
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I would have some gauges put on it to see if the hissing was a refrigerant leak. If the refrigerant is fine then investigate from there.
 
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Old 08-05-10, 02:10 PM
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unit

is it a heat pump? This just might be the reversing valve your hearing....Normal.
 
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Old 08-05-10, 02:28 PM
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Central AC unit hissing sound!!

Thanks and yes it is a Carrier Heatpump but it has been cooling less and less so i imagine that it was losing refrigerant..
 
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Old 08-10-10, 06:21 AM
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carrier central ac

Thanks for the help. I checked the freon and it was at
35 on the gauge so that's good but then I checked the fan
Capacitor and compressor starter. The starter was weak
So I put in a new one and it worked great all night.
This morning I checked but all of a sudden the fan stopped
But the compressor kept working so I shut it down.
Should I also replace The fan motor?
 
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Old 08-10-10, 06:33 PM
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don't just start tossing parts at it

if the fan stopped running with the compressor running too, is that what it should do? Yes it is if you have a head pressure control...You see, unless you know whats normal, its hard to say what is abnormal... The loud hissing sound is normal if the unit has been running for lets say more than a minute and there is no head pressure control or its not working and the internal bypass valve is opening and dumping hot gas over to the low side so that it doesn't explode (code requirements for all pressure vessels)...Is the fan bad??? if the cap is good and there is 208V on the common and run leg of the fan motor leads then the fan is toast. When fan motors die they get hot...touch the body of the motor to see if its hot, only if its accesable without removing the top grill.... with it running and not spinning , try spin the blade with a screw driver, if it resists, replace the fan motor....start there.
 
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Old 08-11-10, 05:54 AM
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Carrier Central AC

Thanks and i just took it apart and started it up and i am almost sure that its the fan motor because i have the voltage from the capacitor and the fan is trying to spin.. I manually tried spinning the fan but it very slowly spins.. I will replace the motor but its going to be tough cause the shaft is rusted onto the fan.. Thanks again
 
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Old 08-11-10, 12:07 PM
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fan blades

check to see if the fan blade is bent or cracked on any of the wings, if so replace it or the motor wont last to long and the vibration can make the unit noisey. use sand cloth to remove the rust and WD40 remove the set screw and squirt it in the set screw hole too. you will likely have to buy a blade puller that pulls on the hub collar only. A cheaper alternative is a tie rod end separator and try to gently wedge it off... if the blade gets damaged, get a new blade... When you install on the new motor, do yourself a favor, coat the new shaft with never seize..
 
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Old 08-11-10, 01:00 PM
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central-ac-unit-hissing-sound

Thanks buddy and it wasnt too bad after i sanded the shaft a bit.. I am picking up the motor and tomorrow. They told me i should buy a new capacitor along with it even though the one i have is good.. I will hope it goes well but i dont think i will have any problems..Thanks again..
 
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Old 08-18-10, 07:03 PM
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Its been a while..

how did the motor replacement go? The new cap is wise, and cheap insurance...
 
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Old 08-19-10, 02:34 AM
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carrier central ac

Thanks for everyone's help. I changed the motor and
And its working great and quiet. The only problem was
Getting the motor cause most of these places are strict
To who they sell to. Thanks again.
 
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Old 08-25-10, 10:00 AM
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In todays economic climate you will find very few supply houses that will object to a CASH SALE
 
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Old 08-25-10, 01:40 PM
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Central AC

Yes i did find one.. Thanks
 
 

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