Wow, the original post here is 3 years old and Nest still has this problem. If the temperature is close to the home temperature, there are chances that the thermostat is defective. He said the furnace was overheating and they cleaned the inside of my furnace and cleaned the flame sensor. So after a day in dual mode, SB’s solution above works! You will often have to press the display and hold it down for about 10 to 15 seconds. It works but the problem comes back after some time. eval(ez_write_tag([[250,250],'voltguide_com-box-2','ezslot_1',109,'0','0'])); Sometimes the C wire in your thermostat may be defective. Once I removed AC issue fixed in minutes! The suspicion was for some reason the Nest was not compatible with my furnace control board, and that was causing the limit switches to fail. Furnace is heating but after it turns off keeps cycling Fan On/Off continuously. Fortunately, we had an extra blue wire that wasn’t hooked up to anything on either the thermostat or furnace end. TL:DR your 3rd gen Nest may require the “C” wire to work properly with your HVAC. I tried to remove the Y1 wire but I get an error code. I also found that the charge on the unit had run way down – not sure if this was a cause or a result of the rapid cycling. It’s loud and it doesn’t heat anything. Your Nest may not be heating due to improper O/B wire orientation, a missing C wire, or because the thermostat is too close to a heat source. The two different technicians that have examined the problem found the limit switch on the furnace board has failed. Because the unit is brand new, I’m returning it and crossing my fingers the alternative EcoBee doesn’t have this issue. If you have a york furnace or any type of Unitarian unit coleman etc… the relay on the circuit board gets damaged over time from running nest in a 2 wire operation. It fixed everything. I didn’t notice it was cycling initially and after a couple hours the Nest battery was dead and the screen wouldn’t turn on. Not good for future business. Enabling this setting along with the Auto-Away setting activates Geo-fencing so that the thermostat identifies your location based on the GPS of your phone. A broken or poorly placed thermostat can cause short cycling. Test the cooling and heating again to ensure that the problem is solved. 2. I assumed the problem was with the Nest, but my husband looked up some info that said a clogged air filter can cause a furnace to short cycle. The only thing I can think of is the Nest Thermostat is causing the blower to run at a lower speed, but even that does not make sense. Check if the Air wave option has been turned ON. Another Denver resident here, we got hit with some sub zero temps this week and i spent several hours troubleshooting why my furnace kept short cycling and eventually locking out. So for all of you with the short cycling, maybe look at other symptoms than the Nest. It seems there are 3 issues here: We have confirmed the 2nd unit (that is short cycling) has enough power (3.86v). This will be a temporary fix correct? Our kids rooms always run colder/hotter than the rest of the house, so this gives me peace of mind that they aren’t too cold/warm at night! It is disappointing as I was looking forward to using the information provided by using the nest. By using the content on this website, you agree to these terms. Glad I found your post, as I experienced the exact same problem at about the same time! Luckily this post was up and the suggestion worked perfectly. Can anyone confirm this? Nest Set Temp: 73 Degrees, Scenario: If you notice continuity, it indicates a short connection. Reverse the O/B wire orientation by following the steps mentioned in the “Nest thermostat turns on AC instead of heat” section. These are: Your Nest thermostat is often 10 degrees off because of a resetting problem, a malfunctioning humidity sensor, incorrect sunblock setting, nearby heat sources, or a network connection problem. A faulty base plate is one of the reasons that triggers this problem. After a couple of calls to Nest support, the second of which actually had me measuring and reporting voltages across various wires with a multimeter, they decided to blame the problem on the “recent cold snap” and mailed me a resistor (200 ohm, 5W) to install as a shunt on my furnace control board (there are tech installation notes on the Nest site that refer to this to aid in the power stealing). I’m have the same issue with the short cycling and the nest is on saying that it is “heating” but furnace does not turn on. Late reply but yes you can terminate two wires under the C terminal screw at the furnace board. Keep the thermostat in a different location that is ideally away from heat sources such as appliances, electrical outlets, and air vents with warm air circulation to mention just a few. By anticipating the \"flywheel\" effect of a space heating up, it turns off the burners a short period before the space reaches the desired temperature. I’m out $14,000 and am afraid to stay in my home. Disconnecting the yellow wire at the Nest fixed the problem. Replacing the limit switch in March worked then – but like I said it failed again about Christmas time. The webmaster of and the author(s) is not responsible for any loss in damages, financial loss and/or personal injury. It has a nice interface, but not the ‘cool’ response that the Nest gets when people look at it. I had this same exact problem! Sure. web browser that Unable to resolve issue with power cycling, even after adding a common wire. nest thermostat turning fan on and off. So I got to thinking some more, and thought as a test, to determine IF the AC unit was faulty AND/OR the Peak Saver timer unit was to blame, I would reinstall my old non-wifi, oldschool thermostat to see what would happen. Nest support said “the common wire was not grounded correctly and the issue was with my furnace”. Why does the Nest thermostat keep turning the AC ON? …I noticed the Peak Saver timer/power interrupter outside, did not show the power light as being ON. Disconnect the white and red wires from their base terminals. It’s been working perfectly ever since. After talking with the Nest technician, he had me feel along the edge of the base for where the head was actually coming from. You can try out the tips given below to turn ON the air conditioning unit with your Nest thermostat. This has helped me out a few times now. In addition, one of the Nest options was set incorrectly, which forced my AC and heater to turn on at the same time even though I wanted only heat. I’ve verified it’s not a power issue, furnace is fine and runs when I swap out with another thermostat. There is a micro-usb port on the back of the Nest that you can use for charging. .. And here I am, a new Nest Gen3 owner, just installed it tonight and it is and has been verrry cold out here in Toronto for many days now… My Nest has been short cycling for hours until I found this post… It was getting cold in here. Remove the Yellow, and then it has no choice. Can I simply add another C-wire on the furnace for the Nest on top of the current AC unit C-wire? With Nest, the indoor fan blower randomly turns off for 3-10 seconds, then back on for few to several minutes. It is a 4 wire unit (Blue/Y1; Green/G; Red/Rc; White/W1). Often, this connection isn’t present in most thermostats. Before installing the nest I had absolutely no problems. I did have a low battery light, but only noticed it the morning after all of this started. Remove the Nest thermostat from your wall. I charged it via USB overnight, but had the same cycling issue the next day. Low level of refrigerant; Missing C wire; Faulty thermostat . 1) Honeywell AT140A1000 40Va, 120V Transformer – 60 Hz You might want to check if the base of your thermostat also needs a replacement. Hope this help. She had me disconnect the C or common wire. due to excess heat within the heat chamber the limit switch is opening causing the heater to short cycle. Two necessary parts were: I spent $575 trying to fix my furnace. This time the AC compressor turned on only during the cooling test and stayed on for the duration of the test. Finally they admitted that this maybe caused by the AC unit since Nest uses the Rh and Y1 to charge the battery….If there is no Y1(AC) because in winter the AC is turned off or not activating due to a Safety switch, it will use the W1 wire….and causes the cycling issue. I took a look at my furnace, and the C wire is wired but goes to the AC unit outside. I disconnected the yellow and the cycling stopped. Hmm, wasn't sure if reversing the Y with RC would cause the nest to mess up or not. With this post; you saved my Nest thermostat’s life…. Not sure what else I can try. I had forgotten, until finding this thread again, and reading my own posts from my original issues from January 2018 and on, that my furnace had originally, a C wire, wired to the AC unit but my old (now current again) thermostat (not a Nest, not a wifi unit) did not need one and after installing the Nest and then after those issues and learning (from here, thank you thank you!) In such cases, disconnect the thermostat from the network for a day and keep a tab on the ambient temperature. This is the second time for me – I went through a round of this in March last year. THANK YOU SO MUCH!! And thanks, you too! Well, make sure it’s fully charged. right, regardless of the battery charge, it still doesnt explain how disconnecting the Y wire fixed the problem. So an update to my Nest experience since installing it in January 2018 and having the furnace short cycle, to then finding this thread to solve the problem (lifesaving, again-continued thanks) by rewiring during the winter to get us through and then the C wire addition to solve the problem and have the AC work.. My furnace was certainly not idle. geofencing). I’m glad to see this post has been helpful, however, at this point I really do think that my problem was a low battery on the Nest. The term short cycling refers to when an AC system’s cooling cycle terminates prematurely only to turn on again after a short time. I am not sure your solution of changing the wiring configuration will work for me. eval(ez_write_tag([[468,60],'voltguide_com-narrow-sky-2','ezslot_21',133,'0','0']));Connect the wire back into the thermostat connector and fit the display. Check if the thermostat is located close to a lamp or any other heat-emitting source. My fix didn’t work this time. So it’s now January 2018 and we just installed a Nest E, and ran into same cycling issue (and the customer service still just recommends releasing the Y wire). Now I’m up and running with two Nest thermostats for upstairs and downstairs. Stefen, could you please explain a little more on what you mean by this? The explanation I got from Nest phone support was that the extreme cold was affecting the yellow wire that runs outside to the air conditioner somehow. This is only a temporary solution for when it’s insanely cold. Called nest support and they think it is a battery issue and offered to reimburse me the cost of installing a c-wire. December 31, 2020 - 5:35 am What the Nest is cycling to sneak power is the power relay, also called a contactor. You can try getting it repaired or have it changed. If it turns on go ahead replace the wires, if it doesn’t your problem may be with your furnace rather than your thermostat (probably should replace the wires here too). Mine didn’t even look visibly dirty so I didn’t think it would help, but it did. After lots of diagnostics and trouble shooting, ended up with incompatible Furnace and AC. It went into a seemingly infinite short cycling loop on January 3rd. This entry was posted on Tuesday, January 7th, 2014 at 10:43 am and is filed under Tutorial. Best guess they have and I can find online is that Nest is stealing power from the furnace via the C wire, which is then causing the furnace to fail. Ultimately, the “solution” was to disconnect the yellow wire. Whoever said it wasn’t a Nest tech, but seemed to have an air of knowledge in the matter. (Supposedly this is due to extreme cold and will work fine once connected in spring/summer?). It is clearly a severe cold related issues. Finally, after no luck with the Nest support lines, I decide to shut off the heat from the app and re-turn it on to 72 degrees. Give that a try and that way you dont have to mess with cooling leg “Y”? Anyways thankful everything is now working especially since the cold weather is about to migrate from the east to the west. This gives it just enough juice to continue operating. Yikes. For example, if the outside temperature is 95 degrees and the temperature where the air conditioner is installed is 65 degrees, the thermostat will be forced to keep the air conditioner running all the time to keep up to the temperature. I performed regular maintenance on both units. One last issue was one of the power wires connected to my HVAC wasn’t properly connected. You can follow the steps given in the section above to do this change. Therefore, the thermostat is likely to sense that the room is already cool and will turn the AC OFF. The solution to the Nest thermostat is the “C” common wire as most recent posts state above. I didn’t read every post so apologies if this is a repeated solution. We had a cold snap here in Toronto, Ontario and my furnace was short cycling. Short cycling is when the furnace will kick on for a few seconds, then shut off for a few seconds, then back on, then back off, repeat indefinitely. Once I did this the short cycling stopped and my furnace kept running. Check if the thermostat is missing a C wire. I don’t not have a common wire hooked up to it. I begin to monitor from mobile app, temperature drops down from 69, 68, 67, 66 however the app shows orange that it is heating to 72 degrees. Reset or replacement needed for the system circuit breaker or fuse. I had issues with me nest last year. Saved me from some frozen pipes! 2. In this case, replacing the compressor is a good solution. Buzzing or clicking sounds at the furnace/boiler/air handler. After calling Nest support we also found that unhooking the AC wire solves the problem but they also were not able to tell me why. Outside Temp: 0 Degrees Fahrenheit Blog Post. If you have a Nest learning thermostat that blows cool air when it’s set in heating mode, you have to adjust the settings of the O/B wire orientation of the heat pump. WordPress. All, great post and actually fixed my problem as well. Pull the yellow wire. I find it curious that a number of us seemed to experience this at the same time though. Found this, but my NEST showed no signs of battery being low. If so, the thermostat is faulty and has to be replaced. I couldn’t find this solution online anywhere, so I’ve posted it here hoping it’ll save someone else a frigid night. No more short cycling. Furnace went right back to normal. Wiring: Y1 black (AC), W1 White, G green, Rh Red. But thank you so much for this post, lifesaving info here rduell! If so, change it to Cool mode. © 2021. so many fast or slow blinks means xyz) that lead me to take that flame sensor out and clean it off a bit. 3. I usually hold down the heat nest for 10 seconds to do a system reset. I wish I had paid better attention to the battery when this was first a problem for me. After troubleshooting I tried this solution out and it’s working: 1. He believes that one of the fuses in the base blew up, but that the heat should go away if I unplug the Y1 wire while they send me a new base. Sometimes, the thermostat may be defective and would need replacement.eval(ez_write_tag([[250,250],'voltguide_com-medrectangle-3','ezslot_6',112,'0','0']));eval(ez_write_tag([[250,250],'voltguide_com-medrectangle-3','ezslot_7',112,'0','1'])); One indication that the batteries of the thermostat are running low is that the thermostat screen is faded or is blank. Lack of a common wire of not enough power may make sense. Tough to say whether the low battery was the cause or the symptom. Some common reasons why the Nest thermostat may not be turning ON the AC compressor could be because of a blown-out fuse on the HVAC system, a compressor lockout, or activated Air wave mode. The Denver area was hit with near and subzero cold and I was visiting my daughter’s family. This could make the thermostat interpret that the house is warmer than it is. Occasionally when I would walk by the thermostat it would say that the wiring had changed. God bless you! You can do this through the Equipment option in the Settings menu. Sometimes, it may be the AC converter fitted to the AC unit that is defective and needs to be changed. There may be a compressor lockout. Hope you have found better service in the future Those service techs that can’t diagnose a dirty filter and high heat rise make me look so much better. I don’t buy into the explanation that it was the colder-than-normal weather. The nest worked correctly on the first try. Same partial solution. We have a Carrier gas/forced air with dual zones (2 thermostats, but only 1 Nest). A heat anticipator is an electrical resistor device mounted in the center of many mechanical thermostats. Both heat pumps were short cycling with the Nests installed, using the old cheap thermostats they both worked fine. In Toronto there is this program, supplied from the hydro company… we have an additional power supply timer called Peak Saver, which will temporarily turn off your AC unit from time to time for about 5 or 15 mins (I cannot recall exactly, at the moment) throughout the day, to help overall power usage and supply an energy-saving technique to help the city’s need for power, especially when many users just keep their AC running, all summer long… Which we do not. eval(ez_write_tag([[250,250],'voltguide_com-box-4','ezslot_16',130,'0','0'])); The Nest thermostat keeps turning the AC ON if it is shorted, if the temperature setting is incorrect, the unit is defective, or if the wiring hasn’t been done properly. Stay warm! So as long as the Yellow wire was connected, even if it was supplying less than ideal current, the Nest base wouldn’t switch over to Red. Changed this now it works like a charm. Unfortunately, I don’t really. It was cold leading up to the failure so the heat had definitely been running (and probably charging the Nest). 5 wires with Aux heating (R, Y, G, W/Aux, O). 1st install went well and nest is operating as expected. If you experience the hot airflow, the problem is with the thermostat. Good luck if you need pro help in Massachusetts call walsh plumbing salem ma 9783043956. Using a Nest without a common wire works on most furnaces. If it doesn’t and you hear a mild buzz from within the unit, the problem is with the unit. I love electronics, computers and everything tech related. Our furnace started short cycling last night and the Nest unit itself was HOT to the touch (and was reading an indoor temperature of 87-ish degrees). As I said, my furnace was short cycling. No disconnected wires necessary. Hi Mike, You’ve probably moved on from this since it’s been almost a year but I thought I’d reply anyway. 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