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notawiz 05-15-2011 03:46 PM

Unbelievable, Thermostat setting changes by ITSELF

Please help… this sounds crazy by my ac thermostat changes by itself !! here is what happens:

Last summer I noticed that my ac been running for a long time so when I go check the setting I found out that my set temp was too low (sometime is 60 or 55.. random) even though I’ve set the temp to let’s say 80. At first I though that my kids been messing with the settings but when I started paying attention and setting the temp when the whole family is not home I found out that the thermostat setting is ACTUALLY changing by itself.

When the problem continued this year.. I said that’s it I will replace the thermostat so I did and bought a new thermostat (programmable & different brand than the one I had) but the problem still there.

I have to mention that my original/old thermostat was NOT programmable. Also, I have 2 ac units for my 2 story home and the problem is happening only on 1 of them.

After I replaced the old thermostats with new one I even tried to swap the thermostats but the problem didn’t follow the thermostat but stayed with the downstairs unit.

I brought a friend AC technician and he checked the wiring and voltages and everything tested OK and he actually told me that he never heard of this problem… and its impossible that it could happen..

I need help…

hvactech126 05-15-2011 04:59 PM


beenthere 05-15-2011 07:12 PM

Wife or kids.

notawiz 05-15-2011 07:51 PM

No guys its not the wife or kids.. I mentioned in the post that I watched happen when I am alone in the house too many times now...

hvactech126 05-15-2011 07:59 PM


Doc Holliday 05-15-2011 09:25 PM

I've heard of static electricity (socks on carpet through fingers) messing up digital stats so would anyone think this could may be touching on what is going on?

Just wondering.

notawiz 05-15-2011 10:03 PM

Doc Holliday: is it possable also that I am getting some feedback current or voltage from the transformer (or whatever supplying the voltage to the thermostat)? that's causing the setting to change?

hvactech126:The original thermostat was a NON-PROGRAMMBLE one that the problem started with ... then is doing the same thing with a programmable one. clearly, its not the thermostat

hvactech126 05-15-2011 10:19 PM

clearly as an experienced professional I have no idea what I'm talking about.... A thermostat can not be changed by anything other than the end user. the thermostat is no more than a switch. It connects wires to send the proper signal for the system to perform said function.

AllanJ 05-15-2011 10:24 PM

A short circuit in the thermostat circuit causing the air conditioning to be on continuously and the lowest temperature the system can achieve is 65 degrees?

Doc Holliday 05-15-2011 11:03 PM


Originally Posted by notawiz (Post 648959)
Doc Holliday: is it possable also that I am getting some feedback current or voltage from the transformer (or whatever supplying the voltage to the thermostat)? that's causing the setting to change?

Any thing is possible at this point as judging from all of these techs who know much more than myself about things of this nature, a stat just dropping set point on it's own is out of the ordinary. You said you changed the stat from the other system in your home and it did the same thing so I would have to believe that yes, something in the circuitry elsehwere in the one system is causing your stat to drop. Not sure how exactly, that feat is not something that is supposed to be possible.

I'm wondering if by chance you have a resistor of some sort on the control board in your furnace causing some sort of distortion. This is all guess work from me as I honestly have no clue if a resistor could do that.

Is the stat that you borrowed from the other system back on the original system you took it from? If not, I'd try putting it back and see how it acts after it's been on the problem system.

notawiz 05-15-2011 11:05 PM

hvactech126: I know what's happening it doesn't make sense not only to you but to me too ... BUT IT'S Happening .. that's why I am posting here to seek an advice from professinoals like yourself, I have ZERO expereince with HVAC but I am an engineer where I've worked with diffrent electronics products and seen some wiered stuff that a noise or feedback currents mess some circuits AND ONLY when you find the real cause, you say WOW .... BUT before that everything doesn't make sense...

notawiz 05-15-2011 11:13 PM

hvactech126: i'll swap the stats tomorrow gain & see if the problem stays with location or follows the stat & will post, I did this test last week & the problem stayed with location.

notawiz 05-15-2011 11:16 PM

BTW: Thanks to evryone here trying to help with thier thoughts, I TRULY APPRICATE IT. Thank you guys.

Extion 07-08-2012 07:22 PM

Just Happened To Me
Has there been any explanation on this yet? This just happened to me.

We have a generic Honeywell thermostadt in our bedroom to control the space heater on the floor. I was in the bedroom taking a nap before work and my girlfriend was on the computer. I had the window open and the fan on because it's pretty warm out right now, and we don't have AC in our apartment.

Well, I got woken up by out bedroom door slamming from the breeze outside and my gf comes in to prop the door open for me so it doesn't happen again. Well, before I could get to sleep, I smell something burning. I call out to her asking if she forgot something on the stove because the smell was getting stronger. She says no and comes in to investigate. She claims the smell is coming from our bedroom, and begins unplugging the fan, thinking that the small motor was overheating or something. When she got down to unplug it, she realizes the smell got stronger, and that it's actually coming from the heat register by the floor. She goes to the door to check out the thermostadt and it's been turned all the way to the right! It's been sitting all the way to the left since it started getting warm after winter! There's no need to have it on!

This is an generic-style thermostadt I'm talking about here. The small, white, Honeywell with the big dial on it. It's not programmable or anything like that. And, we had just bought it last winter, and the dial is pretty firm, not loose or anything. You have to make a conscious effort to change it from off to on, just to be sure everyone understands it couldn't have happened when we went to flip the switch or anything.

The only explanation I can think of is if, perhaps, there is some sort of coil behind the dial with potential to turn the dial when the wall was jostled by the slamming door. I have no other explanation for it.

Does anyone have any other idea how this could happen? Anything other than "it's a ghost"? It's really bothering me because I don't believe in ghosts, lol and I'm not too fond with arguments from ignorance. There's got to be some logical way for this to happen.

And I promise, it wasn't my girlfriend. I already drilled her about it and there's no way she touched it, nor did I sleepwalk to turn it on.

Any info on this would be great since I can't find any other site talking about this. Every search takes you to thermostadts that change because they are programmable. But, nothing like this.


carmon 07-08-2012 09:28 PM

borrow a video camera and set it up.... thermostats normally don't change themselves.... something fishy going on......:eek::eek::eek::eek:

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