Inside the thermostat are three switches/relays. If the thermostat says heat is required, it allows the 24vac to go back on the W wire. If cooling is needed, 24vac is sent back on the Y wire. If the fan should be running, 24vac is sent back on the G wire. If no heat, cooling, or fan are required, there is no power flowing through the thermostat.A Honeywell thermostat will go blank, in case the device is off (there is no power, the circuit breaker had tripped, the batteries are dead), there are issues with the wiring, or the safety switch had tripped. Low display brightness can also be the root cause of the problem. Why Does Honeywell Thermostat Go Blank?. The thermostat might …28 Oct 2021 ... Nest Thermostat No C Wire Problem and Solutions ... Upgrading from a 4 Wire Thermostat to a 5 Wire Thermostat ... - Nest Low Power Fixed. One Hour ...On April 8, a total solar eclipse will be visible across parts of North America, following a narrow track from Mexico through the U.S. and all the way to Canada.. While …1. Check the thermostat's battery levels. If your thermostat’s battery level is low, it will disconnect from Wi-Fi. It does this to conserve power, so it can continue to control your system. If your thermostat repeatedly loses battery charge, it may require a C wire or the Nest Power Connector . Nest Thermostat. 1. Refer to the equipment information. To narrow down possible causes of a “No power” alert, use your thermostat to navigate to its equipment information. If needed, tap the touch bar to wake up your thermostat. Tap again to open the Menu view. Then select Settings . Slide on the touch bar to hover over Equipment . Problem 3: Your Sensi thermostat is not turning on the AC. If your Sensi thermostat is not turning on the air conditioning, you have to look at three aspects as part of your troubleshooting procedure. 1. Possible power outage in the neighborhood. First of all, ensure that there is no power outage in your neighborhood.my bryant programmable thermostat has no power. the furnace appears to still be working, it's just that the thermosat read-out is blank and unresponsive. also, i'm unable to locate the circuit board on the furnace itself. furnace model: bryant evolution system plus 90i Thermostat: bryant TSTATBBPHP01-B any ideas? thank you!The thermostat power issue refers to a situation where the thermostat does not receive the necessary electrical power to function correctly. Without power, the …Coleman Mach thermostat no power. Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts. Coleman Mach thermostat no power. This am I went to turn on my furnace and the tstat was reading 61. Right when I slid the selector to heat it went blank. No power nothing.I had no power to my Honeywell VisionPro IAQ thermostat. The fix was way easier than I thought. Saved me a bunch of money. I couldn't find a solution anywhe...Here is another way to reset the Carrier thermostat-. Start by tapping on the ‘mode’ option on the main screen. Next, select ‘off’ from the options. Now, go to your circuit breaker and switch it to the ‘off’ position. Give it about 30 seconds. After that, switch the circuit breaker back on.Coleman Mach thermostat no power. Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts. Coleman Mach thermostat no power. This am I went to turn on my furnace and the tstat was reading 61. Right when I slid the selector to heat it went blank. No power nothing.Here are more checks a good heating engineer can do: 3. Check the boiler’s internal fuse (or fuses). Most boilers have at least one built in fuse. Others can have 3 or 4. If you have no power to your boiler and have tried the first 2 checks, the next thing to do is to check the boiler’s internal fuses. As a homeowner, this check – and all ...If you don't have a fuse (not all systems do), you may have burned out the transformer. Check the output of the transformer and see if you have 24VAC. If you don't, check the input to see if you have 120VAC present (you should). If you have 120VAC at the primary but nothing at the output (secondary), you'll need to replace the transformer. Upvote.Check the thermostat settings: Make sure the thermostat is set to the correct temperature and mode (heating or cooling). Check the circuit breaker: The circuit breaker for the …Re-insert the wires in case they are not properly inserted. Push the wire as far as it will go by pressing down the connector button. If the connector button remains in its position when you let it go, this means that the wire has been properly inserted. The wire ends may need to be stripped.6 Apr 2023 ... Drain line clog and a tripped float switch shut down a nest tstat. #hvaclife #hvac #hvacservice #hvactechnician #heatingandcooling ...Coleman Mach thermostat no power. Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts. Coleman Mach thermostat no power. This am I went to turn on my furnace and the tstat was reading 61. Right when I slid the selector to heat it went blank. No power nothing.The “No power to Rc wire” message is commonly due to incorrect or loose wiring. Before checking the wiring, first, make sure the HVAC breaker hasn’t tripped. Other reasons for the message include a clogged air filter or excess water build-up in your AC drip pan. Finally, the fuse on your furnace may have blown.Step 2: Check the Pins and Wiring on the Thermostat Base Plate. When troubleshooting a power issue with a Nest thermostat, the first thing you should do is check the wiring. First, remove the thermostat from the wall mount. Then take a look at the wiring connections. Make sure they are tight and any thermostat wires aren’t damaged …Connecting a Nest thermostat to an incompatible system, such as a millivolt, proprietary or high voltage system, won’t deliver the power needed to charge your thermostat’s battery and can damage your Nest thermostat. 4. Check your thermostat’s wiring. Symptoms caused by wiring issues usually occur when you're first installing your thermostat.Central AC Not Coming on - found 3 amp fuse inside air handler blown.Do you buy from Amazon? Support Mikey Pipes by using this link the next time you make a ...There is no power to the thermostat either. Already checked the breakers and the power outlet for the fernace is working. Show More. Show Less. Ask Your Own HVAC Question. Share this conversation. Answered in 8 minutes by: 7/16/2010.Turn off the power to the HVAC system. Check your wiring at the thermostat, making sure that each wire is secure. Check the wires at the control board, making sure that each wire is secure. Turn the power to the HVAC system back on . Then go through testing the system. Testing can be found under Settings > Advanced > …Power . You should check the details of the thermostat and see how many volts it needs and if your power source supplies it. If the thermostat needs 240V and you supply it with 120V then it will surely not work. 3. Battery. Many times it’s the battery that is faulty and replacing it will bring your thermostat to life.Nov 19, 2022 · Check for loose wires. Power can’t flow if connections are not secure. Step 2. Reconnect all loose wires. Loose wires other than the Rh wire can also cause that power doesn’t go to the Rh wire. Step 3. Check your HVAC system’s fuse. A blown fuse stops the flow of power to HVAC components, including the Rh wire. Step 4. There is no power to the thermostat. I've thrown the circuit breakers off and on again, and the fuses are undamaged. The thermostat trouble shooting guide says to the power switches on the HVAC equipment. Are there power switches on Trane 4TWX3 heat pump and the 4TEE3F Air handler and, if so, where?10. Power Issue. If your thermostat is blank and your AC is not working, there might be a power or an electrical connection issue. For example, dead batteries, tripped circuit breakers, and blown-out fuse can cause your thermostat screen to fade out or go blank. Solution: Turn on the power switch.31 Dec 2022 ... Is your thermostat not turning on the heat? It does not fire up the furnace when it is supposed to and the temperature in the house keeps ...AStuf Nest Thermostat Generation 3 • 2 yr. ago. This can happen when the condensate safety switch gets triggered. A slow drain situation does it. Cleaning the gunk out of the system is the normal fix. Other time is if furnace overheats as it cuts power to protect itself. Cleaning the air filters is the first step to correct.To troubleshoot an air conditioner thermostat, identify the type of thermostat that is in use, check that the unit is receiving power and ensure the unit is installed properly. Mos...Turn off the power to the HVAC system. Check your wiring at the thermostat, making sure that each wire is secure. Check the wires at the control board, making sure that each wire is secure. Turn the power to the HVAC system back on . Then go through testing the system. Testing can be found under Settings > Advanced > …A “No power” alert can be caused by the following: The thermostat wiring is incorrect. Your thermostat is connected to a system that requires a C or common wire, but that wire isn’t...It is a tiny switch located on the right side of the unit. To check if it is blown, follow these steps: Turn off the HVAC system. Remove the fuse. Check if the connection at the center is broken. The fuse has a transparent casing, so the wires are visible. If the white, u-shaped wire is broken, the fuse is blown.A massive cargo ship plowed into Baltimore’s Francis Scott Key Bridge early Tuesday, causing the 1.6-mile bridge to crumble like a pile of toothpicks and plunge cars …The “No power to Rc wire” message is commonly due to incorrect or loose wiring. Before checking the wiring, first, make sure the HVAC breaker hasn’t tripped. Other reasons for the message include a clogged air filter or excess water build-up in your AC drip pan. Finally, the fuse on your furnace may have blown.Check to wire if blinking persists. – After Long-Term Use: check wiring or power supply. Green Blinking Light on Nest Thermostat. – Reconnect the display and check the connector pins.-. Press and hold the thermostat display for 10 …A massive container ship lost power early Tuesday before crashing into the Francis Scott Key Bridge in Baltimore, causing it to collapse into the frigid Patapsco …Posts: 42. Dometic T-Stat has no power. Good Day Everyone. We have been full time RV'ers since 2017. Currently live in NW Montana. Most of the problems we have encountered in our Fuzion 429 I've been able to fix. I'm chasing Gremlins now. Last week I noticed the t-stats LED fading and barely readable. The next morning it went dead.Having this same exact problem. Had my Nest for 6 months with no problems, then one day it started doing this. Runs for about 1 second and shuts down, says "No Power". But it obviously has power. The Heater runs fine, just not the AC. I had my buddy come out that's an electrician and he verified that I'm getting correct voltages all over the ...A tripped circuit breaker will prevent your thermostat from turning on your AC. In most homes, the power to the thermostat and the power to the AC unit outside is on two separate circuit breakers. So if the circuit breaker for your AC unit outside trips, your thermostat will still have power. Check your circuit breaker panel for any tripped ...Nov 18, 2021 · No Power To New Amazon Smart Thermostat, see photos. Just got in the new Amazon thermostat and went ahead and connected the blue wire in the T-Stat cable in attic to the large blue wire connected along with the black (float switch) which marked C and connected blue wire to thermostat at the other end as seen in photo below but there is no power ... Thermostats are in every household, but have you ever wondered how they work? Learn about thermostats and take a look inside a home thermostat. Advertisement If you have specific h...Feb 23, 2024 · Firstly, remove the batteries from the thermostat. Secondly, check for any visible signs of leakage or corrosion on the batteries or inside the battery compartment. Thirdly, replace the batteries with a new set, ensuring they’re inserted correctly. Finally, check if the thermostat powers back on. Select Settings. Choose Device information. Use your thermostat to access its equipment details to narrow down the sources of a “No power” notice. To wake up your thermostat, tap the touch bar if necessary. To return to the Menu view, tap once more. After that, go to Settings. Hover over Equipment by using the touch bar.There is no power going to my nest thermostat. V12Tech: Fan ON is the high speed/cool speed. JACUSTOMER-uiq9j0eq- : It says "no power to rc wire detected" V12Tech: Oh I thought it was working. JACUSTOMER-uiq9j0eq- : Nope not working. V12Tech: They were working fine I see. JACUSTOMER-uiq9j0eq- : That’s correct. V12Tech:3. Tripped High-Limit Switch. If your thermostat screen goes blank after several minutes of operation, it could be due to the high-limit switch tripping. Most furnaces have a high-limit switch that prevents the …If you know your thermostat is turned on, then it’s time to investigate a little further. First, inspect your home’s circuit breaker. The reason is because your home’s electrical system is what runs the thermostat. Now, if the circuit that’s powering your thermostat trips, then you’ll have a loss of power. When … See more3 days ago · Different ways to secure the panel for Honeywell Thermostats. 3. Check the Batteries. One of the most common causes of issues with thermostats is the battery running out or being faulty. Honeywell thermostats are no exception. Faulty batteries could be causing your thermostat’s screen to go blank and unresponsive. STEPS TO FOLLOW: STEP 1 – Make sure your HVAC system is turned OFF. STEP 2 – Now carefully remove the fuse. STEP 3 – See through the transparent casing of the fuse whether the center connection is broken or not. STEP 4 – If the u-shaped wire in white color is broken then it means the fuse is blown.Since 2011, households have been using Google’s Nest thermostat. Reliable and convenient, the Nest thermostat is one of (now) many smart home automation devices. Convinced? Here’s ...6 Apr 2023 ... Drain line clog and a tripped float switch shut down a nest tstat. #hvaclife #hvac #hvacservice #hvactechnician #heatingandcooling ...3 Jan 2021 ... Nest E74 - No Power on the RH wire to the Thermostat. It's winter time here in Colorado and not having a working furnace is bad news.27 Oct 2018 ... In This HVACR Training Video, I show How to Troubleshoot the Thermostat for Heat. I Show How the Thermostat is Supposed to Work and How to ...10 Apr 2019 ... The controller is located in the front of the ac unit along with the 12volt and RJ11 4 contact telephone cord data cable. You'll have to remove ...3 Jul 2020 ... How To Check Power at Thermostat - Furnace & AC Won't Start - Finding Loose Electrical Connection. Benjamin Sahlstrom•105K views · 19:56 · Go t...Here are more checks a good heating engineer can do: 3. Check the boiler’s internal fuse (or fuses). Most boilers have at least one built in fuse. Others can have 3 or 4. If you have no power to your boiler and have tried the first 2 checks, the next thing to do is to check the boiler’s internal fuses. As a homeowner, this check – and all ...Central AC Not Coming on - found 3 amp fuse inside air handler blown.Do you buy from Amazon? Support Mikey Pipes by using this link the next time you make a ...Gilad Erdan, Ambassador and Permanent Representative of Israel, questioned why the Security Council “discriminates” among victims, recalling that it condemned the …The thermostat operates between 20-30 VAC, "supplied" to the R/RC terminals and "returning" through the C terminal. A C wire, connected to C on the equipment, is required for the thermostat to power itself. Verify the furnace / air handler door is closed, the power switch is on, and the breakers are on. Confirm you have a C wire in the C terminal.If you know your thermostat is turned on, then it’s time to investigate a little further. First, inspect your home’s circuit breaker. The reason is because your home’s electrical system is what runs the thermostat. Now, if the circuit that’s powering your thermostat trips, then you’ll have a loss of power. When … See moreThe thermostat operates between 20-30 VAC, "supplied" to the R/RC terminals and "returning" through the C terminal. A C wire, connected to C on the equipment, is required for the thermostat to power itself. Verify the furnace / air handler door is closed, the power switch is on, and the breakers are on. Confirm you have a C wire in the C terminal.Mar 30, 2022 · Detach your thermostat’s display from the base to reveal the wires connected to it. Disconnect the Rc wire while maintaining all the other wires as they were, switching the thermostat to heat-only mode. Remove the Rc wire and examine it. Ensure that it has at least 1 mm of copper exposed and that the copper is not bent. It can tell your AC unit to turn on the compressor, powered by a relay that gives 120V power. Since the thermostat is low voltage, it does not have the direct ability like a switch to power 120V. ... With your furnace, there is no 120-volt power. The furnace and the blower motor operate on propane and 12-volt power from your battery.Are you tired of constantly adjusting the temperature in your home? Do you want a smarter, more energy-efficient way to control your heating and cooling systems? Look no further th...Coleman Mach thermostat no power. Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts. Coleman Mach thermostat no power. This am I went to turn on my furnace and the tstat was reading 61. Right when I slid the selector to heat it went blank. No power nothing.1. Check the thermostat's battery levels. If your thermostat’s battery level is low, it will disconnect from Wi-Fi. It does this to conserve power, so it can continue to control your system. If your thermostat repeatedly loses battery charge, it may require a C wire or the Nest Power Connector . Nest Thermostat.Our team can troubleshoot and repair them as well. If your thermostat isn’t getting power, follow our suggestions above and contact us if you can’t get it working. We provide professional HVAC services throughout Southern California. To request assistance, call us at 833-729-9735.The short answer is: There are a few reasons why your air conditioner may not be turning on. First, check to make sure that the unit is receiving power by checking the circuit breaker or fuse box. If the unit is receiving power, then the next step is to check the thermostat to make sure it is set to "cool" mode and that the temperature is set ...Jun 18, 2017 · I had no power to my Honeywell VisionPro IAQ thermostat. The fix was way easier than I thought. Saved me a bunch of money. I couldn't find a solution anywhe... System Switch not set toHeat or cool. Set system to cool or heat an either raise or lower set point below room temperature. Loose connection tothermostat or system. Ensure wires are securely attached. Malfunctioning thermostat. Replace thermostat. Dirty filter. Replace air filter. Thermostat needs a reset.2. Check the Circuit Breaker. If your Honeywell thermostat is still not turning on, then you may want to take a closer look at the circuit breaker. You need to make sure there is power flowing to the thermostat. If there is no power going to the thermostat, then this is the reason why it is not working properly.The “AC Power Loss” message on your Honeywell thermostat indicates that the thermostat is no longer receiving power from the electrical source. This could be due to a power outage or a problem with the wiring or circuitry that connects the thermostat to the power supply. When the power supply to the thermostat is interrupted, the thermostat ...27 Dec 2017 ... Get a Nest thermostat here... http://geni.us/AOcP ---------- LET'S TALK ABOUT LIVING BETTER: ▷ Podcast: https://geni.us/FtGAT4 ▷ My Amazon ...If you know your thermostat is turned on, then it’s time to investigate a little further. First, inspect your home’s circuit breaker. The reason is because your home’s electrical system is what runs the thermostat. Now, if the circuit that’s powering your thermostat trips, then you’ll have a loss of power. When … See moreProblem 3: Your Sensi thermostat is not turning on the AC. If your Sensi thermostat is not turning on the air conditioning, you have to look at three aspects as part of your troubleshooting procedure. 1. Possible power outage in the neighborhood. First of all, ensure that there is no power outage in your neighborhood. Turn WiFi off by pressing Menu→Settings→Network→Wireless, then “ON/OFF”. Leave WiFi off for at least 30 seconds. Select Wireless “ON/OFF” to turn the wireless network back on. If the thermostat does not reconnect to the Trane Home network, power cycle your modem and router. The “No power to Rc wire” message is commonly due to incorrect or loose wiring. Before checking the wiring, first, make sure the HVAC breaker hasn’t tripped. Other reasons for the message include a clogged air filter or excess water build-up in your AC drip pan. Finally, the fuse on your furnace may have blown.22 Jul 2022 ... Comments41. SurferGeek. Since you have a Condensate Pump, it's going to happen again. Buy some HVAC pan tabs (tablets) and put one in your pump ...The exact method depends on the thermostat, but most programmable thermostats have a reset switch or button. This is often located below the main panel of the thermostat or on the ...There is no power to the thermostat. I've thrown the circuit breakers off and on again, and the fuses are undamaged. The thermostat trouble shooting guide says to the power switches on the HVAC equipment. Are there power switches on Trane 4TWX3 heat pump and the 4TEE3F Air handler and, if so, where?Watch this video to see how replacing your existing thermostat with a programmable model can save energy and lower your heating and cooling bills. Expert Advice On Improving Your H...If not, you may have tripped a breaker or blown a fuse on the furnace/boiler control board. Check and verify you have 24v power to the c-wire. Says right on tag, c-wire required to work. Imo, some of those smart wi-fi thermostats don't play well with some hvac systems. raylo32.Connecting a Nest thermostat to an incompatible system, such as a millivolt, proprietary or high voltage system, won’t deliver the power needed to charge your thermostat’s battery and can damage your Nest thermostat. 4. Check your thermostat’s wiring. Symptoms caused by wiring issues usually occur when you're first installing your thermostat.A massive container ship lost power early Tuesday before crashing into the Francis Scott Key Bridge in Baltimore, causing it to collapse into the frigid Patapsco …Ok please read what I am telling you. It is very important you follow my steps or we will not go anywhere. You need to put the jumper at your furnace motherboard. Not at your thermostat. We know your thermostat has no power. We are not dealing with the thermostat. We are dealing with the furnace directly.
A Honeywell thermostat will go blank, in case the device is off (there is no power, the circuit breaker had tripped, the batteries are dead), there are issues with the wiring, or the safety switch had tripped. Low display brightness can also be the root cause of the problem. Why Does Honeywell Thermostat Go Blank?. The thermostat might …. Microsoft365 admin
Check and make sure the blower door is on the furnace/ air handler, make sure the kill switch and breaker to furnace is on, turn the thermostat to fan on does the blower to furnace run? try heat setting does it run? If no, the furnace is not getting power, check door, breaker, fuse on circuit board. thats a few things to check but it sounds ...May 9, 2023 · Step 1. While your thermostat is off the wall and you can see the wiring. Remove the wire from the G connector and insert it into the C connector. Step 2. Go to the air handler and do some changes there too. Remove the G wire from the G terminal and insert it into the C terminal. Y1 can be disconnected due to a safety switch. Exactly. Just to describe how the circuit works. The nest "steals" power to charge by being inline in the Y1/cooling circuit. Refer to the diagram. The 24vAC comes into the nest on R. R connects to the internal battery.STEPS TO FOLLOW: STEP 1 – Make sure your HVAC system is turned OFF. STEP 2 – Now carefully remove the fuse. STEP 3 – See through the transparent casing of the fuse whether the center connection is broken or not. STEP 4 – If the u-shaped wire in white color is broken then it means the fuse is blown.Feb 22, 2022 · Gently pull the thermostat away from the wallplate, remove the battery and replace it with a new one. To tell if your Lyric has AC power, gently pull the thermostat away from the wallplate and look at your wiring. If you have a wire in the C terminal, you should have AC power and your Lyric's screen should not go blank. Apr 26, 2022 · Make sure the circuit breaker or fuse to the HVAC system wasn't blown during installation. The breaker or fuse can blow if power wasn't turned off first, or wire tips touched during installation. Remove the thermostat faceplate and gently check that each wire is well connected. To be sure, you can remove and reconnect each wire. Press on the mode button. For the 8 button models with a door, press the hold and fan mode for 5 seconds and the display will light up. Press up and down at once and the room temperature will appear. Use the up and down key to adjust the temperature. Press on the mode button.Feb 18, 2024 · A thermostat plays a crucial role in regulating your home's temperature, ensuring comfort and energy efficiency. If you're facing the issue of no power to your thermostat, it can disrupt your HVAC system's functionality. In this article, we'll guide you through the steps to diagnose and potentially fix this issue. Take the thermostat off the wall, set voltmeter to "volts AC", and find the wire on R terminal and test from that terminal to any other terminal. Should read 24 volts. Go down to the furnace board and check from C or common terminal to the R terminal. Make sure blower door switch is pushed in. Should have 24 volts.2 Jun 2022 ... Wire the thermostat to the HVAC unit as directed by the wiring diagram. Once you are sure there are no touching conductors, turn on the power ...Opening your Honeywell thermostat is a fairly simple and quick task. There are two different kinds of openings that Honeywell thermostats have. They either have a slide or swing op...If your Amazon Smart Thermostat won’t turn on, you can: Make sure the screen display is on and the brightness is turned up. Verify the main power of the HVAC system is turned on on the circuit breaker. Check that the wires are properly connected. Restart the Amazon Smart Thermostat. Now, if you want to learn to successfully attempt …Step 1: Press the Up Temperature and Mode keys simultaneously for 10 seconds. Step 2: Wait for the rEs notification to appear on the smart thermostat display. Step 3: Hold the Mode button for five ...To check the wiring of your thermostat, follow the below mentioned steps. STEP 1 – Turn OFF all the breakers to which your HVAC system is connected. Disconnect your HVAC system to continue the process. STEP 2 – Remove the face plate of your thermostat to have a clear look at the wires. STEP 3 – Now you have to disconnect the RC wire and ... Thermostat Doesn’t Turn on Heat or Cool. If your thermostat doesn’t turn on the heat or cool you should check the house code on the receiver and the thermostat. They have to match. The house code on the thermostat is set in the setup step 4 while the receiver is set using dip switches. The setup step 3 (zoning) should be set to no. my bryant programmable thermostat has no power. the furnace appears to still be working, it's just that the thermosat read-out is blank and unresponsive. also, i'm unable to locate the circuit board on the furnace itself. furnace model: bryant evolution system plus 90i Thermostat: bryant TSTATBBPHP01-B any ideas? thank you!Wait for it to cool down, and set the temperature lower. If this is a consistent problem, it indicates there is a deeper problem with your furnace, and will need to be serviced by an HVAC technician. 4. Check Furnace Fuse. There is a small fuse on your furnace to protect the electronics from surges.Danny recently appeared on the Emmy®-winning television show Rachael Ray where he used his home expertise to help a family solve their constant battle over control of the thermosta... A no power to the thermostat situation can be frustrating, but with these troubleshooting tips, you can quickly and easily restore power to your HVAC equipment. Remember to check the homes circuit breaker for any tripped circuit breaker, as well as the safety switch on your air conditioner. Make sure the sea wire and common wire are terminal ... Turn off power to your system at the fuse box or system switch. This will help prevent damage to your system and help keep you safe. Pull off the Nest thermostat display. Check that all connectors that have wires are down (see picture). If needed, re-insert wires so that the connector button stays fully pressed down..