AC can't cool house

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  #1  
Old 06-19-13, 06:42 AM
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AC can't cool house

So I live in austin tx and the nights are not getting above 80 degrees and the days are in the 90s outside, but at night the ac is not able to bring it down to 73 deg from about 78 deg. For exmple last night at 8:00 the thermostat said it was 80 deg(after showers and making dinner) when I got up the next moring the thermostat said 77 deg. A little info about the house the ac program is mon-sun 8am-8pm 78, and from 8pm to 8am 73. The house is a two story, three bedroom, 2.5 bath with a attic with blown insualtion. The windows are the engery efficient along with two glass doors. I have lived here for about 1.5 years and last summer it did not do this. So here is my question why is the ac taking 12 hours to cool the house three degrees?
 
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Old 06-19-13, 06:50 AM
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First thing to check is the cold input air temperature from the AC register and the return air temperature. The difference should be around 16-20 degrees.
 
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Old 06-19-13, 06:51 AM
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What is the airflow from the vents like? What is the temp of the air being blown out at the closest vent to the unit and being pulled in at the return? Have you changed filters?
 
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Old 06-19-13, 07:16 AM
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Is your air filter clean? If any of the ductwork is flexible, is any of it squished at all?
 
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Old 06-19-13, 08:18 AM
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Any visible ducts that may have came loose or need sealing?
 
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Old 06-19-13, 08:51 AM
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update on ac

so I looked in to all of your suggestions and here is what I found
ducts appear to be in good shape
the airflow is good
filters were changed at the beginning of this month
The temp of the air going in to the ac is about 78 while the temp coming out is about 70(during this test I set the thermostat to 72)
 
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Old 06-19-13, 11:01 AM
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You need to call a professional, sounds like you've lost the refrigerant.
 
  #8  
Old 06-20-13, 12:59 PM
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Has the Austin Texas area had a lot of rain lately?

A high humidity latent load will cause the sensible temperature not to drop to its normal point.

Has anybody been in the attic since the last time that it cooled okay; or has anything else changed?

The indoor blower wheel blades should be checked for lint buildup & on the evaporator coil; if the blades have any lint buildup the coil will need cleaning.

Check the temperature difference between the return air temperature and then the supply-temperature closest to the indoor air handler or furnace.

Check the outdoor temperature and then check the temperature of the air discharge of the outdoor condenser, then list those temperatures here.

When the humidity is around 50% indoors and around 75F indoors, then if its a 12 or 13 seer condenser the split should be around 16 to 20F; with a lower end split for the higher 13 seer unit.

If the indoor split is low and the outdoor split as high, that is indicative of a high indoor humidity load.

Make sure you have a humidity gauge in your home, if you dont have one get one at a local hardware store; they are low-cost an absolutely essential when checking the temperature differentials.
 
  #9  
Old 06-22-13, 05:16 PM
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ac wont cool

thank you all for your suggestions it ended up be low on freon
 
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