Central Air Troubleshooting

Discussion in 'HVAC Heating & Cooling' started by Buck Shot, May 21, 2008.

  1. Buck Shot

    Buck Shot New Member

    May 21, 2008
    Greetings and salutations,

    Wondering if I could get some expert insight into a little central air issue I just experienced. Here are the details:

    First, a little background: We purchased this two-story home almost five years ago. Have run A/C and heat with no problems until two days ago. Came home and my wife told me the A/C was on the fritz. The compressor (outside the house) would run but we were getting no air flow from the registers. I turned the air on again and sure enough, she was right on: compressor runs but no air flow in the house. Didn't have time to troubleshoot at all until tonight. I checked the Internet and this message board for some advice and started checking things out. First, I tried running the air again. Once again, the compressor ran but there was no air flow from the registers. I checked the air intake near the furnace upstairs and there was *very* little suction. Normally, a piece of paper will stick to the intake register like glue but in this case the suction was barely noticeable. I removed the filter (which I had replaced about four months ago and was still quite clean) and verified there was virtually no air being sucked into the intake.

    Next, I thought I'd try running the heat to see if there was any air flow so I let the heater run for just a few minutes while I checked a few registers for air flow. There was none from any of the three registers I checked, upstairs or down.

    Based on some of the troubleshooting tips I found on this site and elsewhere, I decided to check the furnace to see if I could tell if the blower was running. I turned the A/C back on, and as I was heading upstairs with a ladder, the compressor outside made a real funky noise. I'm not even sure how to describe it. The sound from the compressor got much louder for just a few seconds. Let's just say I thought something very bad was about to happen! Well, interestingly enough, as soon as the noise disappeared (again, within just a few seconds), air started flowing from the registers in the house!!!

    I checked out the furnace and evaporator unit anyway and I didn't notice anything obviously wrong. Granted, I know *nothing* about HVAC, and don't really know what to look for or where to look, but there were no obvious signs of condensation or icing that I could see. For what it's worth, the furnace is a Payne unit, and the evaporator is another manufacturer (forget the name at the moment) that uses R22. Also, we have never performed any maintenance on any of the pieces of the central air system save for replacing the filter a couple times a year. :(

    I think those are all of the salient points but if I neglected to include any key information, I'll be glad to try to supply it. Can anyone shed some light? Is my compressor or evaporator or furnace going to blow up soon? Do I need to start budgeting for replacement units? Any insight is *greatly* appreciated! Many thanks in advance!!
  2. Bill Arden

    Bill Arden Computer Programmer

    Sep 30, 2006
    computer programmer
    MN, USA
    low Air flow would most likely be one of the following. (in order of probability in this case)
    1. Fan needs oil. (even sealed units need oil eventually)
    2. Fan speed controller bad. (but that will most likely not make any air)
    3. Air filter. (but you probably changed it)
    4. Icing. (but that takes time. )

    Things to try.
    1. Turn on the furnace and see if the fan turns on.
    If it does and blows good then it's #3 or #4

    PS: After this air flow problem is fixed... Don't forget to clean the outdoor condenser unit as a clean condenser is more efficient and uses less electricity.
    You can have it professionally cleaned or just use a garden hose to clean it.
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  4. Buck Shot

    Buck Shot New Member

    May 21, 2008

    Thank you for the quick response! Any idea what that crazy sound I heard might have been?
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