AC runs continuously

[Greg M]

I've been having some trouble with the central AC in a house that I just recently moved into. The problem is, the AC works fine, but it won't keep a constant temperature. Basically, when I turn the thermostat to "cool" and "auto" it just runs and runs even after the desired temperature is met. I thought that it might be a bad thermostat, and since I wanted to upgrade to a programmable one anyway, I bought a new thermostat (Honeywell CT3500A1004) and installed it. The AC still does the same thing, I set the temperature at one day 75 when I left for work and when I got home it was down to 68 and the AC was still running. Now I haven't been running my AC during the day, but when I get home the temperature in the house is over 80, so it takes almost the entire night to get it back to a comfortable level. This is my last ditch effort before I have someone come out, any suggestions?

Greg M

[Dr. Hardcrab]

Try putting it on one temperature (say, 75 degrees), hit the hold button, and leave it there. Try that for a couple of days....

[SQLit]

Greg M

Sure sounds like a improper t-stat application. Time to call a licensed contractor.

[JimL]

recently moved into. The problem is, the AC works fine, but it won't keep a constant temperature. Basically, when I turn the thermostat to "cool" and "auto" it just runs and runs even after the desired temperature is met. I thought that it might be a bad thermostat, and since I wanted to upgrade to a programmable one anyway, I bought a new thermostat (Honeywell CT3500A1004) and installed it. The AC still does the same thing, I set the temperature at one day 75 when I left for work and when I got home it was down to 68 and the AC was still running. Now I haven't been running my AC during the day, but when I get home the temperature in the house is over 80, so it takes almost the entire night to get it back to a comfortable level. This is my last ditch effort before I have someone come out, any suggestions?

Do you know how to operate an ohmmeter? Which wires of the thermostat did you wire up?

A quick test using the thermostat wiring will help so provide us with the info above.

[Stormin Mormon]

Sounds like either miswired control wire, or maybe a bad contator on the condensing unit.

Gonna be hard to diagnose over the internet. Might want to call a repair guy.

[cowboy]

you have 2 problems

1. thermostat not wired up correctly is why it keeps running once it gets well below desired temp.

1. if it takes all night to get temp. back down to a comfortable level, then either your A/C system has a performance problem (low freon, high freon, clogged indoor or outdoor coil, etc.) OR your house has inadequate insulation. which problem #2 is, will be determined by the difference in temp. between the vent temp. and the temp at the return.

Greg M

[Greg M]

recently moved into. The problem is, the AC works fine, but it won't keep a constant temperature. Basically, when I turn the thermostat to "cool" and "auto" it just runs and runs even after the desired temperature is met. I thought that it might be a bad thermostat, and since I wanted to upgrade to a programmable one anyway, I bought a new thermostat (Honeywell CT3500A1004) and installed it. The AC still does the same thing, I set the temperature at one day 75 when I left for work and when I got home it was down to 68 and the AC was still running. Now I haven't been running my AC during the day, but when I get home the temperature in the house is over 80, so it takes almost the entire night to get it back to a comfortable level. This is my last ditch effort before I have someone come out, any suggestions?

I wired the new thermostat the same as the old one, which could be a problem if it was wired wrong. The old one had wires in the Rh, W & O terminals. Also, I don't own an ohmmeter, but what wires would I be testing?

Also, when I say that it takes almost all night to get back to a comfortable temp, I mean from when I get home at 6-7pm to when I got to bed as 10-11pm. At times when I get home the temp is around 10 degrees higher than I want it, and being in Michigan it's sometimes pretty humid. It also doesn't help that the thermostat is in the living room, the largest room in the house, and I haven't install my cellular shades yet because I'm still working on painting it. However, the one time I left it on all day, it got down to 68 degrees, it was freezing and there was condensation on the windows.

Greg M