Replies

1. 
   rdesigns | Jun 19, 2013 10:40am | #1

   As you say, this doesn't make sense--the performance of any AC system is dependent (among other factors) on the temperature difference between the outside and inside, or "delta-T" as the pros say. The nightime delta-T  is maybe about 10 degrees (73 inside vs. 83 outside) and the daytime delta-T is likely about 17 degrees or so (78 vs 95).

   The outdoor relative humidity at night will be somewhat higher than during the day, meaning that the latent load is a little higher, but that should not affect the performance in the way you're seeing it, because, wetter air passing over the condenser coil also has a greater capacity to carry off the rejected heat.

   It could be problem with the thermostat and controls. If it's working OK during the day, that suggests that the refrigerant charge and airflows are OK, so the only thing that changes between night and day operation is the controls.

1. 
   tylercc | Jun 19, 2013 11:49am | #2

   Update on ac

    so I checked the temp of the air going in to the ac and I got 78 and the temp coming out of the ac is 70, during this time period the thermostat was set to cool at 72. So does this mean that it is working ok(I am going to geuss not)?

1. 
   rdesigns | Jun 19, 2013 03:37pm | #6

   With a leaving air temperature of only 70, it is not likely a clogged filter, because the LAT ought to be near 55 if the refrigerant charge and pressures are normal.

   A clogged filter (low airflow) would result in an excessively low LAT, along with icing of the indoor cooling coil.

   As DanH suggests, it sounds like you need to call in a reliabele AC company to check it out.

2. 
   DanH | Jun 19, 2013 12:19pm | #3

   From the sound of it, your AC  needs service.  Could be something as simple as a clogged filter (have you checked?), could be low on freon, or the compressor could be shot. 

1. 
   tylercc | Jun 19, 2013 01:22pm | #4

   ac not cooling

   If you mean air filter yes I have checked it, if you are not talking about the air filter, where can I find this filter. what other signs of low freon or a shot compressor can you tell me about. 

1. 
   DanH | Jun 19, 2013 02:18pm | #5

   Ice on the evaporator coil is a sign of low freon (or a clogged air filter).  Sometimes (but not always) low air flow from the AC ducts is a sign of ice.  A shot compressor is generally determined with pressure measurements.

   Also, of course, check that the fan in the outside condenser unit is operating at full speed, and that nothing is blocking airflow outside.  (Check for leaves, etc, in the condenser coil.)

3. 
   tylercc | Jun 22, 2013 08:07pm | #7

   ac not cooling

   thank all it ended up being low on freon

1. 
   DanH | Jun 23, 2013 10:07am | #8

   Keep in mind that if it's low on freon then there's a leak somewhere.  An AC should not leak down that much in two years.