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Central air repair

  1. Jul 3, 2010 #1
    Does anybody here know anything about central air conditioners?

    Mine decided to stop working, and it's supposed to be 100 degrees here tomorrow. Being the fourth of July, I expect getting somebody out to service it will be nearly impossible, or otherwise cost me hundreds of dollars.

    The outside unit sounds like it runs just fine, and I hear something running in the furnace. However, there is merely a trickle of air coming through the vent in the basement, and none reaching the top floor at all.

    Any suggestions?
  2. jcsd
  3. Jul 3, 2010 #2
    You are low on freon and your coils froze up.
  4. Jul 3, 2010 #3


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    If the air itself isn't blowing as it should, maybe it's just a fan. That should not be too expensive, maybe a couple of hundred dollars. That happened to me once.
  5. Jul 4, 2010 #4


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    Low on freon won't ice up the coils enough to block air flow. Low air flow caused by a dirty filter may cause ice to form on the indoor coils especially if the humidity is high.

    If it is an ice over problem you should see some condensation around the outside of the coil box.

    If you are lucky and it is only ice just shut off the outside unit and let the room temperature air blow over the iced up indoor coils. It will melt.

    On the other hand :
    Warm air never seem to feel like it has as much flow as cold air. If you have a thermometer stick it in one of the ducts and hope for 50 to 60 degrees.

    A good indicator to see if the compressor is actually running is to feel the suction line. That is the larger line that comes out of the outside unit. It is also usually accessible at the indoor coil area.

    If the line feels cold the compressor is running.
    Last edited: Jul 4, 2010
  6. Jul 4, 2010 #5
    The last house I was in had low freon and this was the problem.
  7. Jul 4, 2010 #6
    The lineset? You won't be able to feel anything on the insulated line because it is. . . insulated. The return line will be cool, if not room temperature.

    Check to see if your thermostat is properly calibrated and in working condition. sometimes they can be bumped and the furnace will run, but barely pump any air at all.
  8. Jul 4, 2010 #7


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    Low refrigerant is a frequent problem but not the only problem and certainly not something the average home owner could determine or do anything about.

    The first thing for the homeowner to check is the air filter.

    The basic A/C unit:

    Last edited: Jul 4, 2010
  9. Jul 4, 2010 #8


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    Not all units have prefab line sets. Even on the ones that do the foam rubber insulation can be pulled back so a persons finger can be put on the larger line. The small line has no insulation..

    http://www.kbtdel.com/images/ac/ac2.jpg [Broken]

    The unit in the pic above wouldn't pass most building codes, yet there are a lot of them that typically look like this.

    It is of course a good idea to check the thermostat. Most newer electronic stats can't be calibrated, but the switches can be checked. Although since the fan and outside unit are running the thermostat would not likely be the problem.
    Last edited by a moderator: May 4, 2017
  10. Jul 4, 2010 #9
    I turned the thermostat off all night, to give it a rest. I turn it on this morning, and it's no better. Since it's light out, I checked a few of the lines. The insulated line coming in from the outside is soaking wet, right through the insulation, and it's cold. On the outside, that same line has a layer of ice behind the line near my wall.

    Still sound like low freon?

    Any good way to de-ice the thing other than leaving the thermostat off?
  11. Jul 4, 2010 #10
    It is inadvisable to disturb the insulation from a lineset because efficiency will greatly decrease if it is not properly put back. Customers generally are not supposed to mess with units beyond easy troubleshooting (Filter, thermostat, etc) because of the possibility of something going wrong.

    Call a certified HVAC company and have them come look at it on Tuesday. Our company has a free heating/cooling system check-up every spring, so see if your local one has a promotion or anything else going on.

    May I ask the manufacturer of the unit?
  12. Jul 4, 2010 #11


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    The best way to de-ice is to leave the indoor fan switch on the thermostat in the on position. Move the Cool -Off- Heat switch to the off position.

    And definitely check the air filter.!

    If the line was cold and wet the compressor is definitely running. Low refrigerant won't produce ice in that area. The ice has built up because there is not enough air moving over your evaporator (indoor coil). Can you check the fan motor to see if it is running.

    Most fans are required to have a means of disconnecting them from electrical power close to the indoor unit. Usually it is a simple matter of pulling a plug out of an outlet.

    With the power off you can safely remove cover panel on the fan compartment.
    Some fans are mounted on the drive motor. (direct drive) Some are belt driven.

    If there is ice built up on the large line don't turn the compressor back on until the ice has melted. Insufficient air flow over the cooling coil (evaporator) can cause liquid refrigerant to slug back to the compressor and do sever damage to it.

    Some fans are mounted on the drive motor. (direct drive) Some are belt driven
    Last edited: Jul 4, 2010
  13. Jul 4, 2010 #12


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    I didn't say remove all of the insulation ?? Pulling the insulation back just enough to touch the copper tubing is a standard HVAC trouble shooting procedure.
  14. Jul 4, 2010 #13
    have you checked the furnace filter yet, as edward suggested?
  15. Jul 4, 2010 #14
    Low freon was the correct answer. The whole unit froze up. The HVAC is out there right now.

    Since it's a Sunday and holiday, it cost me 250 for him to come out and 200 to put in the freon (plus the time to thaw out everything).

    If it isn't one thing, it's another.
  16. Jul 4, 2010 #15
    Going rate for a journeyman in the sheet metal union is around 79 bucks, so that's a pretty good deal. Freon is also expensive (and dangerous). Good thing you got it nice and fixed up though Jack!
  17. Jul 4, 2010 #16


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    Did he mention fixing a leak?? That is the only way refrigerant can get out of the system.
  18. Jul 4, 2010 #17
    He did not talk about fixing a leak. My understanding is it needs to be "recharged" every so often, like a car A/C system.

    Which reminds me, I've never had that done in my car...

    The guy also mentioned a bad beaker, and gave a quote of 170 to fix that. I need to get home to find all the details; I'm posting from work. My roommates were the ones there.
  19. Jul 4, 2010 #18
    a new circuit breaker runs $5-$10------but if you've never worked with household wiring...

    you need two for the air cond. (runs on 220 usually)
  20. Jul 4, 2010 #19
    Depends on the age. If it is an older unit, she will need to be recharged every so often. But if its a newer lennox, trane, mitsubishi, etc. they should run for their lifetime without needing to be recharged.
  21. Jul 4, 2010 #20
    It isn't new within the last 5 years or at least... that's when I moved in. I didn't bother to check the model. It does say "high efficiency" on the side, so I don't know when that nomenclature came into being.

    Thanks for all the help, by the way.
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