central air unit not cooling, help!

Discussion in 'Shop Talk' started by r.h. in okla., Sep 10, 2004.

  1. It has worked fine all summer exept it seemed to take a long while to finally cool down inside. Yesterday it started not cooling at all. It's blowing air but not cool air. Checked outside at the cooling unit and noticed the cooling line was all frosted up in places where there is no rubber insulation on it. Is this a sign that it is low on coolant or do I have some other problem? Thanks for your help. R.H. in Okla.
  2. Ross

    Ross Moderator Staff Member Supporter

    May 9, 2002
    Sounds like it needs a good compressed air cleaning to me or your condensor fan has quit. Frosty lines are a good sign the compessor is fine and refrigerant is up to par.

  3. oldhoot

    oldhoot In Remembrance

    May 4, 2002
    Ross is right. It could be low on freon but I doubt it. Dirty coils will absolutely kill a units ability to cool. If it's a split system with two parts [outside unit plus the A coil in your furnace] both coils need to be cleaned. The A coil, in the furnace, will circulate inside air thru it and if there's any smokers [or cookin smoke] in the house the cigar smoke/nicotine/grease etc will stick to the coils and then attract ALL the dust/lint cloggin up the coil. I'd guess that that is the problem. Of course if the inside fan is not turnin fast enuff or restricted air flow--that'll do it too.
    Filters need to be replace often! oldhoot
  4. John_in_Houston

    John_in_Houston Well-Known Member

    Nov 26, 2003
    Something like this happened to me a month or so ago -

    Airconditioner was running but not cooling AND the compressor was continually running. What had happened was that the contacts on the relay inside the compressor had welded themselves shut so it was always running.

    This caused the evaporator to ice over so the blower wasn't able to function properly, among other problems.

    I switched off power to the compressor at the switch box and let the ice melt overnight. Next morning I replaced the relay and everything worked fine after that.
  5. Thanks everyone for your info. Is cleaning the A coil inside something easily done or should I call a heat and air outfit. I need to do what ever I can to save money. Thankyou
  6. oldhoot

    oldhoot In Remembrance

    May 4, 2002
    Rh! You can do it if you're careful. On the front of your furnace where the A coil is located-there will be a sheet metal cover. CAREFULLY remove it -makin sure not to bump the refrigerant lines and knock the joints loose.

    Get a light and look inside at the coils. More than likely they will be covered with lint, dust and maybe even cobwebs. Takin a brush -reach inside and brush downward [with the fins] to remove the dirt. If you can't get your hand inside take a brush and tape a stick on it to extend the handle. After you get all the stuff loose take some Fantastic, Formula 409 and spray the fintubes. That will remove the grease and grime. You may need to do it more than once--takin the brush after it each time.

    I've been known to take a garden hose and wash all that goop down into the ductwork where it ran out on the ground. This was only in mobile homes tho. In a house furnace try takin a vacume sweeper and suckin that junk out with it.

    It depends on whether your furnace is a upflow or a counterflow as to the location of the A coil. Upflow--located at the top of the furnace. Counterflow--at the bottom. You can follow the lines to where they go in the furnace and the A coil. Have fun! old hoot.
  7. agmantoo

    agmantoo agmantoo Supporter

    May 22, 2003
    Zone 7
    Here is a check list. Eliminate each one that you have the equipment and skill to perform thus narrowing your possibilities as to the cause.
    Bad indoor fan motor- not running/running slow
    Loose, worn, or broken fan belt
    Bad indoor fan relay
    Clogged blower wheel
    Low refrigerant charge
    Blocked capillary tube
    Blocked orifice
    Faulty expansion valve
    Stuck compressor contactor
    Faulty thermostat
    Extremely dirty or damaged indoor coil
    Once you have everything clean or verified OK, if the problem persists then I suspect that the unit is low on freon. You could take an amp draw check to verify that the current draw matches the data plate and that should indicate if the freon is low. Low current draw equals a low charge typically.
  8. pumpkinlady

    pumpkinlady Well-Known Member

    Sep 3, 2003
    NW PA
    Did you check your filters. Dirty filters are a cheap and easy fix and people tend not to change them often enough. I do think your problem could be the coils though....good luck