Home A/C wouldn't stop running, help

Parent Cafe
1

<p>The rooms are freezing, but the compressor continues to run. The only way for it to stop is to turn off the thermal stat.</p>

<p>A digital thermal meter in another room says 74 F. I have set the thermal stat to 84 F. But it stop to run as soon as I turn the unit back on.</p>

<p>Checked the thermostat heat anticipator which is set at 0.5 - in spec. Clean the contacts with a can of air. I am thinking that the heat of the last several days have kept the A/C running extra long. May be the contact got stuck. What will be a normal range of duration that A/C could run continuously?</p>

<p>What level of difficult would a DIY of installation of a digital thermal stat a DIY job rank? </p>

<p>Any tips and suggestions will be greatly appreciated.</p>

2

<p>Sounds like a problem with the thermostat. My AC runs all day but I have an undersized unit. Bottom line the thermostat should shut off at set point. Call a contractor the thermostat must be wired wrong or bad.</p>

3

<p>Replacing a thermostat is a piece of cake. It’s just four (usually) low voltage wires. About like changing a door bell or a phone. Just find the fuse or circuit breaker to shut off the AC/Heat. It’s four wires, either connected to screw terminals or push terminals. They are usually standard color codes. You can buy replacement thermostats at Home Depot.</p>

4

<p>Is the AC on its own circuit (often it is)? If so, can you go to the circuit box and turn off the power? (that’s what i’d try.)</p>

5

<p>Digital thermostats are easy to install. Usually it is a 24 volt circuit, so its not dangerous. </p>

<p>But thermostats are pretty simple devices, and I would say that if yours has worked ok in the past, its likely to work ok in the future.</p>

<p>If disconnecting the thermostat (turning it off) stops the a/c, you could try replacing it to see if it solves the problem.</p>

<p>If it does not, you may have a problem with the “contactor”, which is the name the a/c business gives to what is normally called a relay. If the relay is sticking closed, then the a/c could keep running even if the thermostat is signaling for it to stop. Your description saying that you can stop the a/c if you turn off the thermostat would suggest that the relay/contactor is not the problem.</p>

6

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<p>Actually, it sounds like a bad relay in the thermostat to me (the thing that goes “click”) if you have your ear to the thermostat when it turns on or off). Turning off the thermostat button to the off position, from either HEAT or AC, is breaking the circuit in pretty much the same way that the relay does when it is working.</p>

7

<p>Changing the subject…was the Stanford Graduation this year? Did you enjoy it?</p>

8

<p>I’ve actually had several thermostats go bad over the past few years. My business landlord sends the HVAC crew out and fixes them very quickly. At home, the oil company comes out and changes them – not a big deal. Probably a simple DIY job.</p>

9

<p>Check with your electric company. Some will install the latest and best gadget for free as part of their save energy campaign.</p>

10

<p>Thank you all very much for your inputs. </p>

<p>So we went the whole night last night w/o A/C - very hot. This AM, I turned it on with the cover off - it works fine. </p>

<p>The cover should have nothing to do with no nothing. But it is running normal now. </p>

<p>I will install a digital one in the next long weekend.</p>

11

<p>If you are talking thermostat for the wall…they aren’t all that expensive and easy to change (I’ve done it all by myself twice, one 3-wire and one 4-wire which says alot since i hate dealing with wires and wiring.) Takes about 15 minutes unless your H is a contractor and he’s looking over your shoulder in which case it takes a half hour to include the yelling.</p>

12

<p>I don’t think you need to wait for the next long weekend to make this change. It will not take three days to do:) I would suggest you buy the replacement tomorrow on your way home and put it in after dinner.</p>

13

<p>Wish there was a like button for post #11 !</p>