Whats wrong with my A/C in my house?

I might have to hire someone but wanted to see if anyone knew what the problem could be here first in case we can fix it ourselves. I have my A/C in my house set to 78-79, but its much colder in the house and the thermostat shows that its 70 degrees. I turn it up to 80-81 and it then it gets too warm, but the thermostat only goes up to about 72 degrees. I dont know if my thermostat is bad or if the A/C is not running properly, but it shouldnt be freezing cold at 78-79 and too hot at 80!. Unfortunately I dont have a portable thermomemter to check the temperature inside the house. How can I tell if the thermostat is bad or if there is a problem with the A/C itself?

Whats wrong with my A/C in my house?
One word...THERMOSTAT. Go to home depot and get a new one
Reply:some t stats have a range diffenrencial if you have the book on it it will tell you how to set it shoiuld be two degrees, if not i recomend a new t stat digital, you can check it out by pulling the y terminal wire off if it shuts off its working if not something elsepossible short
Reply:I would say it's the thermostat. It's an inexpensive easy fix that a DIYer can do.
Reply:Your body is able to tell you when you are comfortable, and the anticapation of the thermostatmay be off or the delay is intermittent, and not working properly. The compressor may not be cycling on demand of the controls, and varies with the designed limits, high head, low pressure, overload, defrost timing, etc.
Reply:The problem is likely your thermostat, like the others said. AC units are dumb....meaning they only come on when told to by the brain (thermostat). Also they shut off when the thermostat tells it to. If the AC unit was broken, it would not be working at all, or the air would only be moderately chilled.





When I run my AC, I always leave the fan setting at ON rather than automatic. Sounds stupid because you would think that it would drive up the electric bill, but it really doesn't. What it does is keep the air from getting stagnant and keeps the second floor from becoming an oven when the downstairs is cool enough to shut of the AC unit.





If you are buying a new themostat, invest in the computer controlled ones that you can program. These can be set at different temperatures for different times of the day for economy. These can be very expensive or affordable. The only real feature that matters is an adjustable timer. It will pay for itself within 3 or 4 months if used properly.





I almost forgot to mention. If you already have an electronic thermostat, change the batteries before buying a new one. Low batteries can have all sorts of wierd effects in computer controlled equipment.
Reply:If you do not have a digital tstat,gently remove the outside cover,should be able to lift from the bottom on rectangle stats or grasp it at the 10 and 2 oclock position for round stats and pull out/downward.See if there's a dust buildup on the bi-metal strips that hold the mercury bulbs in place,if so,tale a straw or something similar and blow the dust out,if you have a digital stat,it needs replacing
Reply:Your problem is simple (at least for me lol). Your thermostat is only accurate to about +/- 5 degrees. Now some are more accurate depending on how expensive it is.





To fix your problem, without knowing what type of system you have, you can simply buy a new thermostat and install it. You will save quite a bit of money if you can do-it-yourself.





To change the thermostat you need to turn the power off to the unit first. Then look at how your old thermostat is wired. Wire your new stat the same way and then mount it to the wall. After all the work is done turn the power back on to the unit.





The standard wiring for an air cooled split system is wired as followed. Y=yellow wire (cooling) G=green wire (fan) R=red wire (24 volt power) W=white wire (heating) and sometime there is a C=?? wire (common).





The only way you can get in trouble is to hook up the common wire incorrectly and introduce power. If you need more information you can email me.
Reply:Generally, if the unit is blowing cold air then the a/c itself is fine. If you don't feel that the thermostat reflects reality it probably needs to be looked at. Like most mechanical / electro-mechanical devices it can get out of calibration, especially if it took an accidental shot by being bumped into. You'll probably have to call a technician, but it shouldn't take but 5-10 minutes to fix.


Inside most thermostats is a mercury switch locked in place with a screw. Loosening this screw enables the mercury switch to be rotated slightly changing the point at which it closes the circuit. Move it one direction it comes on earlier. Move it the other and it takes longer to switch on.





Good Luck.