The air conditioner keeps working even though the temperature set on thermostat is reached inside the house?

Question

The AC in my house keeps working even though the temperature set on the thermostat is reached inside the house. Could that be because there is a connection problem between the thermostat and the AC unit itself? Any suggestions and/or recommendations would be welcome. Thanks

Answer 1

I know there is at least a plus or minus one degree range with my thermostat. The digitals are so accurate that if they "say" like 72 they could mean 72.5 and keep cooling.

It might have to touch 71 before kicking off.

So take it with a little grain of salt.  BUT if you are saying you set it at 75 and it goes to 70 AND both the condenser and air handler are shutting on and off at the same time, it sure sounds like bad thermostat or the red and yellow thermostat wires are touching someplace.  

You could remove the red wire off the thermostat when it won't stop running and if it stops then the problem you are sensing is at the thermostat.

Good Luck

Answer 2

Shut her down at the"off'setting on the t-stat and see if she cycles off.Wait 10 or 15 minutes,before turning it back on,set your temp to 75 and turn it back to the "cool"setting at the t-stat.Let her run for awhile and see what the inside temp is and run the t-stat above that temp to say,78 or 80 and see if she cycles off.If for any reason the outdoor unit continues to run,when performing these simple tests at the t-stat,the contactor is stuck in the outdoor unit and will have to be repaced.

Keep one important thing in mind.Most t-stats will read differently when compared to another thermometer by 4 or so degress one way or the other.An expensive and fancy t-stat is no better than the mecury ones that have been used for 50 yrs.so don't go and waste alot of money on an expensive one.Should you choose to replace the stat.

Good Luck.

Answer 3

If you crank the set temperature way up (say 85F), will your a/c unit stop working?

If the a/c cooling just fine, you may want to get a new thermostat. A new programmable thermostat is what I would recommend.

Answer 4

your fan relay is burnt out you need to have it replaced. What it is doing is staying open, this will cause all the problems you are talking. Everyone else is just guessing. You will have to change out your fan limit switch this is located in the furnace area. Your limit switch and fan relay are combined so you will have to change it out. If you go into your furncae you will see like a dial with wires going into it you will need to unplug one of the wires and this will turn the unit off. Probally be best if you called a contractor out to do this or if you are handy it isnt something that is to hard to do. Good luck.

Answer 5

You may be putting too much faith in the accuracy of the indoor temp. gauge on the thermostat, or it could mean that the thermostat is NOT operating properly to shut down the a/c system when the 'set' temp. is reached.  Are you sure that the control isn't set on continuous blower and that it's THAT that keep running all of the time, while the compressor unit outside might be shutting down for periods of time?

Answer 6

You probably need the thermostat recalibrated, or worse, replaced.

Answer 7

If your thermostat has a mercury bulb these thermostats have to be level or the settings will be off.

Often they are not secured well and will get out of position.

Answer 8

If you had a connection problem the unit probably wouldn't run.  The tstat probably needs calibration or replacement.  But then again if you are going by the little thermometer in the thermostat, sometimes they aren't very accurate.  Are you sure the ac is running and not just the fan?