If you notice the air coming out of the vents isn't as cold as it should be, then there could be any number of causes for this. Regardless of the reason, it generally means that an important component in the equipment is not working properly. When it comes to air conditioning system, one faulty part can affect all the parts, and eventually the whole system collapses. Some symptoms may include a weak thermostat, a clogged air filter, or other factors outside. You may also need refrigerant in your system.
Air Circulation is Weak
If the air is not flowing properly in your duct system, first check the unit to see if it frozen up, in which case, thaw it out, change your air filters, and then turn it back on. Low air circulation could also mean that your air ducts are dirty or that they are blocked either internally or possibly an item lying on top of them. Check the air ducts in your attic to make sure they are completely open. If there is blockage somewhere in the unit, then it's time to call a Efficient Air & Heating expert to get the problem fixed immediately.
The System is Noisy
The simple fact is some air conditioners are loud or will have a tendency to squeal from time to time. If you're turning on your air conditioner for the first time after months of it lying dormant, it may have to operate a few times before running smoothly. If after a few initial runs, however, you're system still seems louder than normal, then you may need to have your motor belt checked. Most older units that still use belts, will need them changed periodically in order to insure smooth performance. Another cause may be the bearings which help run the fan in good condition.
System is Freezing Up
There are basically 2 reasons why an air conditioner freezes up. The most common reason is blocked air flow. This almost always begins with a dirty air filter. One rule of thumb to remember is that air filters have to be changed on a regular basis. While some filters need to be changed monthly, others can last up to six months. Regardless of what type of filter you may have, you need to set reminder to change them often. Another possibility is that you have a leak somewhere in the refrigerant line. If this is the case, then you need your refrigerant line changed out immediately as this problem worsens in a short period of time.