# Unbelievable, Thermostat setting changes by ITSELF



## notawiz

:wallbash:

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…


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## hvactech126

ghosts?!:surrender:


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## beenthere

Wife or kids.


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## notawiz

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...


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## hvactech126

It can not happen..... USE A NON-PROGRAMMABLE STAT BY HONEYWELL.


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## Doc Holliday

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.


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## notawiz

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


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## hvactech126

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.


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## AllanJ

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?


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## Doc Holliday

notawiz said:


> 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.


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## notawiz

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...


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## notawiz

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.


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## notawiz

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


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## Extion

*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.

Thanks!


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## carmon

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


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## Extion

carmon said:


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


We've lived there for two years and this is the first instance of something like this happening. Is there no mechanism in the thermostadt that could allow for it to move on its own if the conditions are right?


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## Red Squirrel

I'm not of much help, but I thought I'd share a funny thermostat story I heard at work.(phone company)

One time they got a trouble ticket, the customer said every time someone called them, their furnace would start. The tech was like "whaaaa?!" So he goes over to check it out. Someone had hooked up the thermostat wire to the phone line somehow. LOL

Maybe your thermostat is hooked up to something it should not? lol


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## Extion

Red Squirrel said:


> I'm not of much help, but I thought I'd share a funny thermostat story I heard at work.(phone company)
> 
> One time they got a trouble ticket, the customer said every time someone called them, their furnace would start. The tech was like "whaaaa?!" So he goes over to check it out. Someone had hooked up the thermostat wire to the phone line somehow. LOL
> 
> Maybe your thermostat is hooked up to something it should not? lol


lol. No, no, it's an Honeywell, non-programmable, analog model. The connection is quite simple. Im just wondering of the coil inside could somehow "buckle" from the heat, or somehow exert some force on the dial?


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## Extion

Trying to go about this logically has only brought me to one other conclusion. I'm assuming the thermostat has been on cranked for quite some time, and we just hadn't noticed since its been so hot in the apartment that it just didn't trigger the heat register (as it would give the distinct smell of turning on that we just haven't experienced until today).

Being that today was much cooler, when the breeze came through and slammed the door, it displaced the air enough to trigger the thermostat to turn on, giving the effect that someone had turned it on today without anyone being around.

However, the problem still exists knowing that nobody has come to visit that would have played with the thermostat, and that neither me or my girlfriend have touched it since turning them off after the winter months.

Although this sounds more logical, it still doesn't make any sense...


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## scottmcd9999

Mechanical thermostats can get out or whack at times and need to be recalibrated, but generally those recalibrations are just a few degrees - not nearly enough to significantly alter the settings. Could have simply been that, or someone could have inadvertantly bumped it up while cleaning, walking beside it, carrying something in the room, etc etc. I can beleive a digital tstat could do what is described earlier in this thread - turn on by itself, or move settings up/down - but a mechanical thermostat requires physical movement to alter settings.


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## Joyce58

For all the non-believers, this has happened twice to my daughter in the past year. She mentioned it to me to see if I knew why but since it's never happened to me, I didn't know. I told her I'd check around on the internet to see if it's happened to anyone else and I was disappointed to see that most of the pros in here think it's a hoax. I guess I'll check some other areas to see if I find the same thoughts. Good thing it's not an issue that need corrective action asap.


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## jagans

Yup He's an Engineer. Cant spell "their"

Before I went to colage I count efen spell enkneer, now I are 1.


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## fa_f3_20

This is a fairly common problem in the home automation world. It's caused by trying to use an electronic thermostat without a common wire back to the transformer. Lots of older installations either didn't wire a common to the thermostat location, or didn't connect it at the transformer.


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## scottmcd9999

Many electronic stats don't have a common wire, and are powered by batteries. Regardless, as I said earlier, it's certainly conceivable with a digital/electronic stat, but not with an older analog stat.


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## beenthere

scottmcd9999 said:


> Many electronic stats don't have a common wire, and are powered by batteries. Regardless, as I said earlier, it's certainly conceivable with a digital/electronic stat, but not with an older analog stat.


Seen 2 T87F thermostats that set the temp higher by themselves. When ever the heat would come on. As the bimetel would move it would also move the dial up just a little, and over the course of 2 to 3 days it would increase the temp setting by 4 to 6 degrees.


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## emort520

How weird... my thermostat has has been overriding the settings by itself. I have no idea how it happens. There is only the two of us and I wake up first (usualy by the sound of the heater blasting). Its set at 66 and I wake up to it on at override 70. Its so weird, makes me feel better someone else knows what im talking about. Also my stove keeps switching to the timer by its self as well ... who knows. Im just worried its some type of electrical issuse in my house.


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## ben's plumbing

we have seen some programmable t-stats get screwed up in the process of setting itself during the operation of adjusting itself...replace stat...ben sr


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## eirk

Please tell me there Is a fix I left my house for a few days set ac at 87 to avoid coming hometown a hot house 4days later came home to a cold nous ac was set at 75 today I baritone set at 80 all day not 5 min ago I walked by its at 75 grrrr I cant afford my ac running all the time


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## operagost

Well, since you posted here instead of starting a new thread, you probably read most of this discussion. Make sure your thermostat is wired properly (at least two wires should be connected inside, normally), and replace the battery if it has one. If those check out, replace the thermostat.

I imagine you'd know if your thermostat was programmable, but in case you just moved in (or you're a renter), see if your model of thermostat is programmable and turn off the program. Most programmables let you override, but then cancel the override after a set time (like two hours for cheaper Honeywells) and/or when they hit the next setpoint in the schedule. 

Also, please slow down when you type!


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## Russ Shepard

*Mysterious Thermostat*

Don't know about what all you "experts"say, but this has happened to me three times. Honeywell thermostat with numbers 0514 and T822D2550, non digital non programmable type. Bought this house over a year ago, and this just started happening. Two times during the night the thermostat has moved over to make the heat run longer, one time we woke up to 85 degrees! The third time, the thermostat control had moved all the way to the cool side, keeping the heat from coming on at all. This thermostat controls the heating unit only, no a/c, and no on off or auto settings. No kids ,wasn't bumped in to. This only happens overnight...I think my house is haunted....


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## ben's plumbing

ok then after all the comments here..we all agree replace the t stat...ben sr:laughing:


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## yuri

I dunno, Have to check the ole crystal ball. Could be a episode of "The Zone" Bwahahaha


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## bradentucky

*same thing only worse*

okay dokie, regular window unit. model number.FAC127S1A

ya i should have started a new thread. w/e .. anyways

the thing constantly changes from "cool" to "energy saver" to "fan only" some times really fast like a constant sequence of "beeps".. sometimes just one or two beeps (beep meaning it changed settings). and it only does this in the area that controls those three settings. the Temperature doesn't change nor does the fan speed.. the friggin thing will wake me up in the middle of the night with a flurry of beeps and i have to refrain from tearing it out of the wall only because there would be a hole in the wall, plus no ac in FL.... but i think im getting close to understanding what's going on here... either there is a short. ie dust build up on the board. or it wasn't wired right to begin with..or i need to find the circular battery thats on one of the boards .. one of those 2032 batteries and replace that i have the thermostat chip hanging out by the wires so i can press the buttons on the actual board instead of having the plastic cover over it because i thought the case was fitting too tight and maybe that was the prob but nope.. still ghost changes with it off.. soooooo replace the thermostat?


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## Schmitt03

*unbelievable thermostat*

By chance have you ever figured out what the problem was? We have the same exact thing happening at our house.. Love how people jump to a conclusion with out knowing the truth or facts. Im very interested in your findings.. Thanks


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## Relosach

*thermostat with its own mind*

We also have the same problem...our thermostat on the AC changes itself with a continual barrage of beeps...help!


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## yuri

Electronic thermostats can go haywire/malfunction just from age. Average life is 10 yrs.

Mechanical thermostats should not change their setpoint unless the mechanism inside is very loose. The heat anticipator should not be creating enough heat to expand it. If it is then you have a serious current draw problem from the gas valve.

Get a new Honeywell Focus Pro thermostat from HDepot.


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## Relosach

Thanks Yuri, but I live in Taiwan...no HDepot here and probably no Honeywell Focus Pro thermostat...time to call the technicians in....thanks again!!!


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## Relosach

Our AC went bonkers when the typhoon hit the other day....and has been bonkers since...


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## yuri

Probably had a power surge and it damaged the circuit board.


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## Deborah Peel

My thermostat ( manual thermostat) is changing temperature settings on it's own aswell. Came home this evening and thermostat was set at 90%. I live alone. All doors locked. 😕


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## KittyK

hvactech126 said:


> 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


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## KittyK

Well, professional, SURPRISE! My thermostat changes without me touching it. My little dog can't reach it. When I get up in the middle of the night, it feels warmer in my apartment. I always set my heat at 72 degrees. Many times when I get up the setting is at 75 degrees.


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## roughneck

KittyK said:


> Well, professional, SURPRISE! My thermostat changes without me touching it. My little dog can't reach it. When I get up in the middle of the night, it feels warmer in my apartment. I always set my heat at 72 degrees. Many times when I get up the setting is at 75 degrees.


The member you quoted hasn’t been on this site in 7 years. 
You’d be best to start your own thread. 
Very hard to make any suggestions without knowing what you have.


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