My air conditioner kicks on but the thermostat won't go below 79 degrees.What is the problem?

Question

the filters have been changed too

Answer 1

Not sure exactly about your question.

Do you mean the THERMOSTAT won't go below 79 or the house TEMPERATURE won't go below 79?

If you mean only the thermostat setting then with some thermostats you likely have it set on "auto" rather than cool. In that case you can't set the cooling temp too close to the heat temperatue (like within 5 degrees). Otherwise it would cool then heat then cool and so on.

So if the problem is with the thermostat then you need to lower the heat setting to a cooler temperature or switch it to "cool" on the heat-auto-cool switch you find on heat pump type thermostats. (They often use those types if you have a different back up heat even if not a heat pump).

Good Luck.

Answer 2

Al's answer was close, but close only counts in horse-shoes and hand-grenades.

An Air Conditioner will create a 20 degree drop between inlet air temp and outlet air temp when operating correctly.  Compare the air temperature at the inlet (suction) and the air temperature at the outlet of the air conditioner.  If there is a 20 degree difference, then your A/C is operating at it's limit.  If your house doesn't get cool enough, then the A/C simply doesn't have the capacity to cool your house as quickly as the sun is heating it.

Now, buying a new, larger A/C would be the obvious answer...  but might not be the only answer.

First, check the air path for obstructions.  A clogged air filter can greatly reduce the efficiency of an A/C.  Replace the airfilter and if possible, clean the cooling coils with water and mild soap.

Next, look into increasing the efficiency of your house's insulation.  A couple new roles of insulation in the attic can greatly increase your house's ability to hold the heat out and the cool in.  Check for gaps around doors and windows... fill them with weather stripping and/or caulking.  Also, UV reflective window tinting or placing window shades outside your windows can greatly reduce the amount of heat transfered to your house.

Finally, run less heat-producing appliances during the hottest part of the day.  You would be surprised just how much heat is put-out by TV's, Lights, Dish Washers, Dryers, etc.  Run these things at night when the temperature drops.  Also, Switching from incadescent light bulbs to those mini-flourescent bulbs can reduce heat.  A flourescent producing the same light as an 80 watt bulb consumes only about 15 watts...  20% power consumption means 20% heat production.

Finally, if none of these enhancements helps, then it's time to look at buying an A/C with a larger capacity.

OH, and do NOT use one of those fans with water in them (portable evaporative cooler AKA swamp cooler).  Humidity decreases the efficiency of your A/C.  It will have to work much harder to get the humidity out of your air before it can cool it.

Answer 3

You might need some freon

Answer 4

Air conditioners will only cool 20 degrees lower than the outside tempurature.  If it's hotter than 99 degress it won't get cooler than 79 degrees in the house.

Obviously, you should make sure the AC is operating properly.

Answer 5

Try cleaning the filters, and vacuuming the coils...