Why does my central a/c not cool to the thermostat setting?

Question

It ran for 24 hrs yesterday at setting of 76 but never got below 78. It has been 80 in the house while set at 76 when it is very hot outside. Filter is clean. Any suggestions?

Answer 1

OK , from a pro. CALL A PRO.

Did your system ever work right?

When is the last time you had it serviced / cleaned?

Could be low on refrigerant but it would have a leak that needs repaired.

Could be dirty indoor coil / loss of airflow, needs a pro to check.

Outside unit can be full of dirt, grass, algae, which will cause it to not be able to give up the heat it picks up from inside.

No matter where you set your thermostat, once its cooling, you can turn it down all you want and the air coming from the ducts will not change in temperature.

CALL A PRO, don't call uncle Billie Bob's heating and lawn care.

This is a comfort product, pay the $100 service call to find out what is going on and get comfortable.

Answer 2

Several questions come to mind. What is the outside temp.? Is air moving freely from the vents? Is the house insulated? Have you had a HVAC tech check your system? Is your heat exchanger iced over or plugged up by algae? Does the compressor come on outside? Have you closed the vents in infrequently used rooms? A contractor can answer these questions and the cost is more than offset by the increased comfort and efficiency.

Answer 3

Is the unit itself clean? ... If it's an outdoor unit, the vent-slats have to be cleaned as well.

Also... the way your A/C works may not be strong enough to keep up with the heat outside... if it's REALLy hot, your A/C may hit a cooling threshold ... that would cause your A/C to run 24 hours.

Call an HVAC guy to come out and clean the entire system (or you can take the chance and remove the cover from your outdoor unit and do it yourself) ... shouldn't cost more than $50.

Answer 4

well, when you set a tempurature on your thermostat, the ac actlay is blasting out alot colder air because it has to keep a larger area cool, and somthing inside the a/c tells it what tempurature to blast out when you set it to 76, but if thats broken then if you say 76 then it will only blast out 76 making the house as hot as 80, i no this because its happened to me before

Answer 5

The vents may need cleaning, or the compressor may be failing. Perhaps the system doesn't have enough capacity to handle the size of your home when the outside temperature rises too high. Have it checked by a reliable service company.

Answer 6

The most likely answer is a combination of temperature differential setting adjustment (normally three degrees), and overall inefficiency. It may be that your house is poorly insulated, and that you are unable to keep up with the demand of loss, or possibly dirty coils, condenser obstruction, check your filter, and vacuum out the squirrel cage and coil if possible.

Answer 7

a/c units are designed to run, your unit could be put on a heavy load due to high heat and high humidity, make sure your filter is clean like you already stated, coils are clean, have an HVAC tech come out and check charge after doing a little preventive maintence yourself.... but good possibility its undercharged, dirty, or high load not being able to keep up..... good luck 10 yrs in field

Answer 8

could be a freon leak or it could be frozen

Before you call a technician out and pay for service, try turning it off for a few hours (overnight would work well) and letting it defrost (if it is frozen). Then turn it back on and it may cool off better. If that doesn't work, you should call a technician to check it out.

Answer 9

you could have a freon leak and are low on freon. You will need to have a service person come out and hook up guages to find out. He may be able to recharge your system but you may also need a new ac unit if the leak is too bad.

Answer 10

You might be low on freeon, so you are not getting cool air. Also, your house may be pooly insulated, and the cool air is getting out, the heat from the outside is getting in.