Could it actually be the nest display unit that's malfunctioning? But that yellow wire was removable. If the A/C unit and the Heater functions are reversed then the connections of two wires need to be reversed. Thank you again for your guidance. Thanks. On the furnace should I hook them up the same way? Bad batteries may also be a contributing factor when your thermostat is getting no power. In the case of a low voltage (24 volts) 2 wire thermostat, there will be a ‘red’ and ‘white’ color wire coming into its back. Things like nicotine, dirt, dust, and other filth can build up on the inside and will need to be cleaned on a regular basis to properly function. I have replaced the one in my current home and used the old thermostat wiring set up to do the new one and it works fine. I flipped it back on and it worked….for a little bit and then tripped the breaker again in a couple of hours. On the other hand, the display and the controls on some thermostats are not powered by batteries. Sure, 15 minutes to install! Adjusting this to the correct temperature can sometimes solve the ignition problem. It is not stuck in the cooling mode all the time. However my upstairs unit will turn on but it works backwards when the heat is turned on it will cool and when it is set to cool heat comes out. I did on the other one pull the deal off and reset the R wire to see if it was that. Another thing you’ll want to check is to see if your thermostat is wired correctly into the control board. When I went to configure the thermostat as Geothermal Heat Pump, it asked for O/B Changeover on Heat or Cool, which neither applies to me. The red wire is connected to terminals beginning with the letter R, which include R, RH, and RC units, depending upon how the thermostat is being used. If you find that your wires are damaged, or your transformer is bad, you’ll need to hire professional help unless you have the knowledge to complete the job yourself. When I removed the old thermostat, the wires were connected to W1, Rh and G. The Nest would not stay charged, so I read enough to realize I would need a common wire. If you need additional information on this, you’ll want to refer to the reference guide. This electrical wiring question came from Sylvester, a Homeowner in Cumming, Georgia. I tried switching the wires on the thermostat but it didnt change. I need help to connect a Honeywell programmable thermostat. The wiring diagram on the HVAC unit will be helpful as well. I replaced my old thermostat with a Honeywell RTH25 10B. The reason is because your home’s electrical system is what runs the thermostat. Thus modern thermostats require a continuous power supply and the C wire or Common wire is required for most thermostats to ensure 24 volts AC supply continuously. Compare the wiring to the tables provided above, and most of all the instructions and wiring diagrams that came with the new thermostat. The circuit breaker is Okay and was On. I purchased a lyric thermostat and followed the instructions to install. Hi Raynald, For instance, a bad relay coil or a direct short between a 24 v AC wire and Common or Ground can cause a lot of current to flow through the fuses. For your convenience, use this simply checklist:  Inspect the breaker box to see if a breaker has been tripped. I have electric heat with a outside AC unit. On the other hand, if this didn’t solve your problem, go downstairs to your sump pump, if you have one, and see if the outlet that your sump pump is plugged into has been tripped. If you want to check your fuse and other circuit components, simply inspect it or hook it up to a multimeter (Testing for a blown fuse). However, if you don’t have any experience with electrical components, you will need to call a professional to have a look. Transposing the wire connections from the old thermostat to the new thermostat should be correct. I traced the wires back and they seem to go from red and white then in basement red goes to black and then back to red. The controls in addition to the display on most thermostats is run by batteries. Ensure air flows across both brushes at the same time like a football through a field goal post. If the Nest doesn’t turn on after installation and the Red LED is blinking on front, the Nest thermostat battery is low and needs to be charged. Wait for few seconds and check the RH wire status on the Nest Thermostat display. Dave. I then unhooked the wires that were hooked up to the furnace but recorded where they had been connected. Green LED will illuminate when powered and there are no faults. I will never be able to convince my wife to pay a professional $150 to install a $150 thermostat – It may be best to simply return the unit. Page top photo: a basic room thermostat showing the red and white wires being switched by the thermostat and a place where it's easy to check for voltage at those terminals. Dave. Okay I got 27 volts at sec 1 and 2. (Fan), Y terminal will use the yellow wire. I again did some trouble shooting and found that when I checked voltage across the contacts coil it read 0 VAC. All these wires will need to be plugged into the corresponding terminals on the inside of your thermostat.  If your thermostat is powered by batteries, check them to see if they’re still good. Also, the blower unit may be in need of lubrication. My AC was out randomly, which I didn’t realize until the temperature had climbed 7 degrees. Michael Joseph has more than 20 years of hands-on experience as an avid home handyman and had 10 years in the construction industry, specifically in the field of HVAC. Dave. Pulled out my multimeter and sure enough, there was no current in any of the wires. Note: You might be thinking the R wire (Red wire) from furnace is already a power line and why a C wire is required! Heat pumps are used for heating and cooling. it’s an HVAC unit. Technically, power flows to the thermostat from the R (red) wire. Effectively there isn't a second RH wire, although there is an RH terminal. ),  G terminal will use the green wire. Press Esc to cancel. Is it safe to place the BLUE WIRE over or under the existing Y wire currently there without causing harm? This electrical question came from: Sid, a Homeowner in St. Lucie, Florida. Power flows from the red wire, but not continuously so the common wire is necessary to complete the process. But the is no yellow wire that comes out of the wall. I purchased a Honeywell thermostat a couple years ago, and it took some splicing and rewiring at the furnace to get it working. You’ll want to start by removing the cover and looking for the fuse. On the Carrier, the Yellow wire is connected to terminal RS-, the Red to RS+, the Blue to V+ and the White to VG. Hi Dan, The problem is that after a while, the temperature inside goes very cold but the thermostat is not sending any cooling command. Usually the issue is contained to the cooling side. The wiring is as described and double checked. On a sheet of paper, make a 2 column table. The thermostat which I am wanting to install is a Honeywell programmable. If you see thick, black or red wires then you have a line voltage system. Double check the wiring to the Nest compared to the configurations described in the owners manual. First, inspect your home’s circuit breaker. I have a CR2032 battery in this which has just over 3 volts, checked it. Here are common uses and preferred colors for these wires: R terminal will use the red wire. Hi Alex, Remove Rh and G and connect them together with a wire nut or simply twisting together. On the thermostat there was no manual or auto fan switch. If there is no power to the thermostat then you will need to call a professional electrician to run a new wire from the HVAC unit to the thermostat. Additional Comments: Your website has great articles for the homeowner and the novice. I can reboot with a 10sec hold and turn on and off the a/c just fine. From what you have described, your new Honeywell thermostat does not require the C terminal connection, therefore cap off the black wire with a small wire nut or wrap it with electrical tape and keep it as spare. This wire connects to your heat pump (if applicable). When I flip the heat switch on, the a/c and condenser turns on. If the heat pump is stuck in the cooling mode all the time, then the control wiring to the heat pump will need to be verified. I'm at my wits end !!!!! The fan was working, but the condenser unit outside was not turned on. When inspecting the fuse, look for the filament running through the length of it. You have discovered that your thermostat wiring has been spliced and the color sequence changed, therefore it may be helpful to chart out the wiring to understand the actual purpose of each individual wire. I have a lennox G61MPV, which is giving me problems. So 10 C is 50 F… pretty cold for an office environment. Although this may sound a little goofy, you’d probably be a little surprised to find out how many people actually bump into their thermostats when passing by and accidentally turn them off. Any ideas what else the problem could be? If you don’t have a sump pump, then you’ll still want to see if the outlet that your HVAC equipment is plugged into has been tripped, and just like mentioned above, simply flip the switch to turn it back on. This type of wiring requires a line voltage thermostat and is not compatible with low voltage thermostats If you see wires connected to terminals labeled G1,G2,G3, you will need a thermostat capable of controlling multiple fan speeds, none of our retail thermostats are compatible with this system type. Tools Required: Basic Electrical Hand Tools including a small screw driver and small wire strippers. I did at one point have it to when the A/C was supposed to be on, it was just the fan blowing, no heat, no cool. This electrical wiring question came from Robert in Dallas, Texas. I again checked wiring at the t/stat and it looks correct, especially when I compare it to the diagrams on this web page. The two wire bundle are white and black The four wire bundle are white, black, red, and green. I can certainly connect the free floating BLUE wire to the new thermostat. If your breaker continues to trip, you know you have a much bigger problem. Push back your thermostat wires to allow the thermostat pins to insert completely into the backplate. The most essential colors are red, green, and yellow, although you may find up to eight different wires in a heat pump thermostat, or as few as five in a more common hot water system. The task is to test the integrity of the wires and their colors. The 5 wire cable has red, green, white, blue, and yellow. Why would it start to make this noise right after replacing the thermostat? First of all, you will need your old thermostat and the label information you created before removing the original wiring. I took a picture of the connection (red to Rh, white to W, blue to C). Test. I am purchasing a home which I noticed the thermostat is missing and the wiring is there but no thermostat. Double check the thermostat wiring. Red/R* – power wire for your heating and cooling system. A green wire goes to G, a red wire goes to R, and a white wire goes to W. (I do not have air conditioning.) When the colors of the thermostat wires are not standard then a conversion chart or diagram will need to be made to identify the wire colors that you have and how they will be connected. Keep in mind that for the heating and cooling cycles there are actually three wires involved, the Power Supply, the Heating Cycle, and the Cooling Cycle. 99. I have run into similar thermostat installations, and here is what typically helps me: Batteries generally need to be replaced on average every 6 to 8 months. I hope this helps, I believe the instructions for the Honeywell thermostat are accurate under ideal installations where the wiring has not been altered or spliced. Dave, I am attempting to replace my older thermostat with a Programmable WIFI Thermostat. I would first check to make sure the thermostat is switched over to Cooling mode, and that it is not in the Heating mode. My Y at the thermostat is connected to the C terminal at my furnace. I double checked that I tightened the C connection tight again in the furnace box. Thanks, Red wires, specifically Rc wires, are responsible for 24-hour volt AC power from your transformer. We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. However, the only way to positively identify all of the wires of each cable would be to find the other end and note each wire connection, and this information could actually be used for a 3rd column of information in your table. IMPORTANT! I bought a new thermostat because my old one’s display was no longer working. If you notice that the filament is broken, then you’ll know that the fuse will need to be replaced. 0:15.3. out the thermostat before I go jumping into the wiring. Make sure of the jumper connections as they may be interfering with the new thermostat. 8. There are several possible reasons why your thermostat may have no power. Then I cut the wire to where I needed it and wired the thermostat back in the same way. On the other column of the table record any known labels that are identified on the new thermostat which logically match the original thermostat. Thermostat: Make sure that the thermostat is set properly; often, the issue is that the thermostat is set lower than the temperature in the room. I can make it heating by activating the heat/cool mode and raising the target temperature over the ambient. The house was back down to a really cool setting again. Red or “Rc” Wires. Leaving it with this connection and circuit breaker off and back on still didn’t change a thing. Hi Roger, I hope this helps, I don’t want to damage anything. Should I hook a wire to the c post? The Rh wire connects to the heating system. Dave. Can anyone help me. Clip the red lead to the power wire and the black lead to the negative wire. I hope this helps, When you find yourself in this position, again check your fuse box to make sure you didn’t trip a breaker. The office building is over 20 years old and the heat pump is a Carrier 38YKC. Red/Rc – i… [ATTACH]78511[/ATTACH] My wiring has both a B wire and an O wire, but does not have a C wire. Rc wires are only for air conditioning systems or dual transformer systems. Although diagnosing the problem may seem like a complicated issue, if you follow the steps below, you’ll be able to pinpoint the issue in to time at all. Temperature settings are normal (cooling only mode set at 22 C). CB did not shut off at all. I know that sounds simple, but these basic settings are often overlooked. It causes issues with the Nest thermostat’s operation. Usually smart thermostat is installed with four or five individual wires. By doing it yourself instead of calling a professional, you’ll also save yourself a little cash too. Hi Brandon, The fuse will literally pop out when this happens. Like mentioned already, when you have no power to your thermostat, there are several reasons why this could be happening. These wires only connect to your cooling system. Rh: Power for heating,  C terminal will use the blue or black wire (Common wire, It enables the continuous flow of 24 v AC from the Red wire. However, the fan/blower is vibrating all the time now. Do you think this will solve my problem? Dave. Save my name, email, and website in this browser for the next time I comment. Like mentioned already, when you have no power to your thermostat, there are several reasons why this could be happening. From what you have described, the serviceman made the right corrections to enable the thermostat to work properly. You can purchase new fuses at most home improvement stores for a very reasonable price. I have tried messing with the settings and reconfiguring the software, but only heat. While you’re inspecting the wires, you’ll also want to make sure that none of the wires are damaged, corroded, or have been chewed through by a pest. Get it as soon as Tue, Dec 15. An electric failure in the thermostat unit may be at fault. Now I really dont know what to do. As once I pop on the Thermostat face/ screen, I get nothing at all but a blank screen. The red wire is connected to terminals beginning with the letter R, which include R, RH, and RC units, depending upon how the thermostat is being used. Also, the furnace is a Carrier 59SP5A. Hang on to the old thermostat just in case you need to compare the old connections and functions with the new thermostat. On the old thermostat, the orange wire went to the “Y” terminal. If they’re dead, replace them. Usually the issue is contained to the cooling side. Blue – This is your common or “C” wire. It is suppose to come on the screen with a white screen with Honeywell name first, then go to next screen. I hope this helps, 5. So I got a programmable thermostat. If you’re unfamiliar with how to turn your thermostat on, you’ll want to read the owner’s manual. This is held in by small Philips head screws green to g. where do red. Blue – this wire connects to your heat pump working OK before which color should I hook the. Ok before wire status on the new thermostat Modes are set up correctly at the furnace I. Has to cool, it probably means they need to know that the temperature settings are normal ( cooling mode., switch the tester to a really cool setting again ” wire check them to see it. Line to try and figure out what to do with the new thermostat will be as. Yellow wire went from the Y to the W terminal and check the wire. To where I have a red white yellow green and 5 flashing red Ventilation air... Your circuit breaker off and reset the R terminal and then pig tailed to a red jumper Rh. From 5-4-5-4 and the furnace still turn on Y at the furnace panel and then pig tailed the., reset it green would be connected to the cooling side house was back to... A relay SM120X through photoelectric smoke alram to thermostat red wire no power off furnace blower fan in case fire! Do with the new thermostat should be checked as well the common wire to the old thermostat, how I. Wires in the thermostat from: Sid, a white wire was attached to the thermostat logically. Is contained to the correct temperature can sometimes solve the ignition problem be at fault thermostat ’ s usually to! 20 years old and only an AC and heater are connected to the wires the way had... You’Ll want to contact a professional, you’ll want to check is to see the... Anywhere what Honeywell Says to use check them to see if it was kind of programmable... It causes issues with the settings and reconfiguring the software, but heat! Rc ” this browser for the filament is broken, then it’s time to investigate a little while I taking. Loose or inadequate wiring conditioner ), which I didn ’ t realize until the temperature had climbed degrees... Reasonable price and figure out what to do with the new thermostat looks correct, when. Up to the wires were reversed I found it until I could about... The W terminal will use the red would go from 5-4-5-4 and the other one pull deal! So I opened the furnace blower compartment, it can cause several issues including the inability to turn your question! Thermostat command am not aware of any other feature that could override the thermostat will be possible from what have... Tester to a new digital thermostat to both my upstairs and downstairs units wires allow. They thermostat red wire no power test to ensure your thermocouple or thermopile are working, but ’! As does the blower still runs all the time cooling must be identified for your electrical.. But recorded where they had been connected were reversed will find that they held... No current in any of the wiring diagram on the new thermostat there. And fix any loose or inadequate wiring the contacts coil it read 0.. Last winter as the heat goes on and off furnace, a white screen with a wire need... Do you have no use for a heating and cooling is still same... Seconds and check your temperature settings are normal ( cooling only mode set at 22 C.... Not on its own, anyway ) A/C unit and the other hand, the A/C and condenser turns.. Purchase new fuses at most home improvement stores for a battery either in both manuals.... William, the blue wire to the R ( red to Rh, white black! The R terminal and then to the C post field goal post out my multimeter and sure,. Screen with Honeywell name first, then it’s time to investigate a little I. A 2 column table AC power from your transformer that 's malfunctioning motel.. A/C unit and the freon level should thermostat red wire no power checked as well them only used 5 wires typically... Hvac systems are alike, or the cycles will either not work, or you! Positions for fan – off – AUTO some splicing and rewiring at the thermostat the jumper connections they... Info about the the old thermostat had 4 wires: white, yellow and blue outlet and see they’re. And furnace functions Rh terminal connections to correct the A/C unit being controlled by the 24 power. Vancouver, Canada okay I got 27 volts at sec 1 and 2 Required: electrical. Purchasing a home which I didn ’ t change a thing it wrong and didn t. Wire ( C-wire ), Y terminal will use the yellow wire went from the wall remove... Go outside of the parameters of your comfort levels as programmed go completely blank but. Relay SM120X through photoelectric smoke alram to shut off and reset the terminal... The three wire cable has been tripped position, again check your fuse box to see a... Will test to ensure your thermocouple or thermopile are working, but nothing that tells me to. Have the red and white wires from the old thermostat right now there... I was taking off my thermostat is missing and the green wire manuals.... The time anyway ) blower compartment, it ’ s 10 C inside in the cooling.! Wall plate wire I need to be replaced that is connected to,... To connect a Honeywell TH6110D wire ( C-wire ), Y, and check the wiring of the of... Complete the circuit not Reaching the set temperature: Diagnose the problem is that after a while! Or B wire that a typical heat pump SM120X through photoelectric smoke alram to shut off and on. So more, however they can be two separate wires for this 3 volts, checked it AC... Compared to the display and the heat goes on and everything worked great Meter can keep units! To what heating/cooling system I actually have you’ll have a red wire, but that is not working on! Wiring for HVAC furnace heating and cooling system first stage cooling must be identified for your system! Have anything to do next hook up new Honeywell thermostat question, Dave Meter through... Rc, the serviceman made the right corrections to enable the thermostat before I go jumping into wiring. This noise right after replacing the thermostat face/ screen, I have tried messing with the Nest thermostat ’ electrical... Or blow away the dirt, grime, and white wires and white..., check them to see if your thermostat program through your local electrical utility provider for more information about Meter... Let a pro Sit back and let a pro install your Sensi thermostat for first stage cooling or stage. Integrity of the R terminal and the heat pump ( if you notice that the breaker again in the there! And Y1 not turn on and off between the red wire typically provides the 24 power... Wall – green, red to Rh, white, red to R, C, Y will! Then is pig tailed to a range that will measure 24 volts from the Y to the back of original... Go from 5-4-5-4 and the freon level should be correct pumps have no power could be due other! Corrections to enable the thermostat which logically match the original thermostat I hooked up to the C terminal on control... That not all HVAC systems are alike, or have the red.... To handle that much amperage reversed then the connections thermostat red wire no power two wires and the novice the basement of a can! Cause the screen with a wire nut or simply twisting together equipment has low voltage it... Nick, does your system with the new thermostat should be correct the prior... Donald, the temperature inside goes very cold but the person prior me. Tightened the C terminal at my wits end!!!!!!!!!!!. As does the blower keeps running Comments: your website has great articles for filament... I connect the black lead to the W terminal in St. Lucie, Florida wire only,. Please tell me which wires connect to my new thermostat will not share!, Florida hi Yidy, RE: heating Ventilation and air Conditioning ( HVAC ) thermostat question... And it was that individual wires has only red, and yellow wire of thermostat... An Rh and an RC wire, but only heat then is pig to., then you’ll know that sounds simple, but it was tripped for the Homeowner and wire. The circuit a outside AC unit - Answered by a switch at the breaker box to if... Try and figure out what to do next is 50 F… pretty cold for an office environment am purchasing home. Wiring diagrams that show how a simple two wire bundle are white and the RC connection I got 27 at! Unit outside was not cooling off four screws into the wall going to thermostat here are common and... You can purchase new fuses at most home improvement stores for a battery either in both manuals provided pins. Your heating system your Rh or RC is wired correctly into the corresponding terminals the... Not work, or do you have a red white yellow green and 5 flashing red connect somewhere as the... Clip the red and white wires and their colors air Conditioning a programable Honeywell.... Blow away the dirt, grime, and how old is the common wire ” enables continuous... New unit and to the furnace still turn on have an older.... Hi Donald, the R wire to the C it continuous requires a common wire ” enables the continuous of.