C Wire -- How to use the G wire as a C wire

[@michaelpinto8421]

Thank you for putting this video together. The instructions were easy to follow and able to be adjusted for my new Honeywell Home WiFi Thermostat and Carrier Gas furnace. The adjustment of the G wire to C port and bridging the Y and G ports on the furnace performed exactly as expected. Appreciate the time put into this.

[@sbsk2009]

Just got done installing two Honeywell WIFI Thermostats requiring C-wire using the method described on this video, and it works perfect. Almost returned them when I did not find the C-wire. Thank you Homehandyman101.

[@biggestbattles]

Thank you for this video, it saved me a service call! My Nest thermostat was installed by a 3rd party in the winter. It worked fine, but when it came time to turn on the A/C, the compressor would come on, but the blower (fan) wouldn't. I thought it was a bad circuit board... until I watched this video. I inspected the control panel on the furnace and I saw that the installer moved the G wire to the C wire, but there was no jumper between Y and G. After jumping those two connectors, everything worked perfectly. Thanks again.

[@Brook.klassen]

I had this same problem so I added the jumper wire and it is still not working? Is there something else that you did?

[@ballpython3310]

@@Brook.klassen so funny thing about my system and why i hesitate to use this method right now is that my fan works and there is nothing at the G spot, so the fan is wired in somewhere else, your system is probably the same.

[@GaryVolts]

Good video but you might point out that with this trick you'll be giving up independant control of the fan to use just as circulation. I live in a 2 story house and it's really useful because the warm air tends gather upstairs leaving the down stairs cold without it. So it's a trade of having to mess with batteries periodically versus independant fan control.

[@andreapinto2089]

Thank you so much, you saved me! I had tried everything and could not get a c-wire to work by using an extra wire, but this did work with my new Wi-Fi thermostat period thank you so much!

[@MrFreerangebeef]

Worked perfectly! I'm using a Honeywell Lyric T5 WiFi thermostat with 4 wires. Instructions from Honeywell did not work. After following this video's instructions the AC, at first, didn't turn on. However, the thermostat did a self-update/calibrate thing and it has worked great since then. Thanks!

[@HairAffairBellamia]

I did the same but you cant manually control the fan ,

[@stefanmagyar4042]

Excellent instructional video that helped me saved a device call for my Nest thermostat on my gas furnace. Thank you very much.

[@sballinger86]

Appreciate the video, it was very helpful but I am having an issue maybe you could help with. I have a gas furnance, and conventional Air Conditioning. I swapped the G wire to the C terminal and jumped the G and Y terminals and things worked great. I did this in winter however so while I was able to get heat I never bothered to test the Air Conditioning, now that it is getting warmer out I cannot get my air conditioner to power on via the thermosta

[@njco4life]

I understand about the G wire going to the "C" connector and the jumper wire. My question what do you use if your furnace does not have "C" spot?

[@BrianHSC]

Sometimes, it's called Common or Comm. If you don't have those either, than get a new furnace.

[@brazukabiker6566]

Very nice. It worked perfectly, my thermostat had 4 wires without c wire, I was installing a Hire wifi thermostat. I did how was instructed. Thank you .

[@samifarhat7029]

First off this was so helpful for my ac!! Now I bought a condo and have a similar issue where the heat is turning on and off with a nest that was previously added. Would this trick help for the heating as well?

[@Homehandyman101]

Turn off your breakers to the HVAC system, then check the C wire to see if it is firmly connected at the furnace. At the tstat, make sure the wire going into the C terminal is stripped back enough to make a good connection.

[@lmd569]

This is a GREAT Video!!! I will lose the option to have a fan only mode my using the G wire, but my fan will turn on if my heat & ac run..Correct? I have Both heat (oil furance to forced hot air) and A/C (using the same air handler for hot air) on the same thermostat. Just jumping G & Yat the air handler will turn the fan on in both cases?? Thanks!!

[@kimconor]

Thanks for putting this video together. It is great. However, I have an issue. I have an oil furnace in my basement, and an air conditioning system in my attic. My G wire is connected to the air conditioning system in the attic. I looked in my air conditioning system, and I don't have a C terminal in there. I have the following terminals in the unit in my attic: R, W3, W2, W1, G, 3. And there are currently wires connected to R, G, and 3. Can you help?

[@ravisel]

I followed the instructions mentioned here as even though the Cwire was connected to the furnace but it did not come out to the thermostat. After doing this my heater works fine, but I am not able to turn ON the AC. What am I doing wrong? I am OK with not able to run the fan by itself.

[@countryside8122]

ok...what about a heat exchanger. Can you also use the G wire on BOTH g and c? I would like to use a the fan as it helps move the hot air from my wood stove that is another room.

[@kevinsmith9355]

I need to know this exact question

[@bretth2005]

Works great for new smart thermostat in older house. Thanks

[@mfasouletos]

I have a carrier unit...seems newish....I can't find where my wires trace back to...Anything i can do or look up to see how this is hooked up?

[@johnl2613]

Question, what are the white and red wire that are connected to the C terminal in the furnace? I opened up my furnace and I see that a red (can't tell if it's exactly red) wire (not the one that connects to the R terminal) is connected to the C terminal and a white wire is connected to the Y terminal. These two wires are from a separate brown wire that apparently connects to the compressor (???). There is the main brown wire which has blue (this is for the Y terminal in my setup) , Red, white and green wire.

[@larry24cohen]

Is there any way I can still run my fan alone? At times, I like to keep the air circulating in my house without the heat or A/C on. Thanks in advance.

[@ryandunbar1314]

No AC from vents after new wifi thermo. My antique Smith boiler has no such setup and the AC unit is up in a closet on 2nd floor. I could see no Terminal block on AC unit behind panel to do this either. I'm at a loss but I'm sure I need a jumper somewhere. Heat functions fine it's just the AC fan that's the issue now. Compressed working. help is greatly appreciated

[@johnalbrets6504]

I have a heat pump only and there is no "C" terminal on my air handler. There is 24v across the green-to-red and blue-to-red. Why can't I just connect a jumper from either green or blue to the "C" terminal on my thermostat?

[@chiyookeynes3007]

like the features, setup was difficult for some of my devices (August Door lock, kzbin.infoUgkxhB5YOMNj04GuoAosExygP4cH-dKeb4aB Bose speaker)... but all switches and outlets (5), thermostat, tankless water heater. Unfortunately all I can do is turn on/off Bose. It doesn't support volume or changing channels, but I believe that is due to the particular speaker I have.... Worth getting if you already have other devices to use it with... I don't sit around and ask Alexa questions much so that doesn't really matter to me....

[@deseandegarno8791]

Thank you so much you saved me hundreds

[@Cyruxx11]

I have an old tstat and bought a Honeywell Wifi. But when i took out the old one i saw that only have W and B wires. What Can I Do power up the tstat. Thanks

[@wulution]

i recently put in a wood boiler. i have to turn my blower on and off manually. i would like the blower on my furnace to turn on and off by my thermostat. can you help me please?

[@zaccor]

I noticed you had a wire already in the C terminal at the furnace, which I gather goes to the AC unit. My furnace control board looks exactly the same. So when you switch the G wire over you just put it together with the wire that's already in the C spot?

[@klyons20]

never heard of a 3 tell me what color wires are connected to what on the t stat?

[@abelroks1]

i have a carrie weather maker 9200 would this method work to fire up furnace thermostat click on but furnace won't?

[@caitlinsticco8008]

Hi! We seem to have two-transformer wiring system where the Rc and Rh wires are entirely separate power supplies for the AC/fan and the gas boiler, which doesn't seem to use the fan. Will this trick still work? I think not, right? I'm guessing the thermostat would only run power through the Rc wire if it was running the cooling system, right? So the circuit the G is on isn't even relevant in our case?

[@acoustic4037]

May I ask what circumstance would put you in the position where you want to lose manual control of the fan just so you can say you have a c wire at the t-stat? Only compelling reason I can think of is if you don't want to use batteries at the t-stat.

[@darjluke]

acoustic4037 Generally the reason is because you have a thermostat that requires the C Wire. Newer ones without batteries or rechargeable batteries like the Nest. Most people don't run their fan alone. If they did, they would clog the filters really fast. Then again, most people don't change their filters. I have a honeywell wifi that I tried this with and all I could get was heat, the ac would not start. It may require both C and G wire.

[@acoustic4037]

I guess there are thermostats that could require a c wire, but there are other options available. I would not advise buying a thermostat that creates a problem when there are plenty that don't. If running the fan would plug the filter, then it would be an improvement in indoor air quality and should be done. In heat pump land (the south) tenants let the filter get plugged, and the coil sees no air, and the coil freezes up all the way outside to the condenser unit. People think they should change filters on a time schedule or worse, not at all. Filters should be changed when.... they're dirty. If you live in a glass house with no pets or dirt, you can go a year but most people with 5 dogs, 24 cats etc need to change filters every month.

[@JamesMooreSeattle]

+acoustic4037 Never in my life have I just run the fan. Not once. I don't think I even knew that was a thing until a year or so ago, and I'm 49 (grew up in San Diego, in a house where we had neither AC nor heat). I'm happy to give up that fan ability to get a thermostat I can use with something like ZWave that's going to require power, since the only use (for us) of a thermostat is to turn heat on and off in the winter.

[@3dsman]

Burned popcorn in the microwave? Run the fan.... Doing a construction project in the house creating sawdust, etc? Run the fan... Have allergies that are bothered by vacuuming? Run the fan... Temp outside's nice enough that you really don't need heat on or cool on, but want to feel a bit of air movement? Run the fan... I can't count the number of times I've run the fan without the heat or cool engaged just to move air in the house through the filter for (see above) a variety of reasons. I'm looking to add a new-fangled WIFI tstat but I only have 4 wires, my current unit is 'smart' and gives me all functions including the fan, so I'm a little tweaked that the new WIFI tstat from Honeywell doesn't allow me fan control. I don't mind putting batteries in every few years. Worth it.

[@AJ-xd1vl]

Hello - my AC guy switched the G to C for me in my thermostat and my furnace however now there is no Air at all coming from the vents when i turn on AC. Is it because I dont have a jumper from Y to G? Is this a necessary step?

[@nateLegakis]

Can you turn on the fan without heal or cool with this method?

[@sundaymorningroll]

No. By 'scavenging' the G (fan) wire you lose the ability to control it as you described.

[@EricS-gi5jl]

What would happen if you use the G wire as a C on an electric furnace? I believe mine is wired this way but im having cooling issues. Could this be the reason?

[@thomaslantis2544]

Hello im working with a old Honeywell 2 wire red and white no c ... Downstairs on furnace I have (w j 4 g x y) with white goong to w and red going to 4. Where can i run a wire from to thermostat? G?

[@dm19609721]

If one does this can you still operate the fan manually???? I sometimes use the fan even thought the A/C or furnace is not operating.

[@seamuswarakomski9203]

nope you will lose the ability to control the fan independently

[@seamuswarakomski9203]

buy a "wire saver" module and you will be able to keep all separate functions, or go the best route and run new wiring. I always install 8-wire thermostat wire in case a wire shorts or breaks in the wall OR if you end up deciding you want to add any humidification or additional stages of heating or cooling in the future

[@dm19609721]

Thanks for the info.....I just went with 18/5 thermostat wire and ran it through the walls.

[@wilymlen1426]

this is the issue I am having also, the Thermostat works great but we have an HRV and would like to run the fan separately. Are there specific instructions on how to do this? I can't seem to find info on how to do this. Thanks for your help btw.

[@brabusx2]

i do have a C wire but i don't get it won't power up my thermostat... is there something wrong?

[@james-mi2pq]

I have a C wire that is not connected and the PC board does not have C terminal. Can I connect it to frame ground

[@HippiehavenCanada]

Got new tstat with these terminals...Rh, Rc, w, y, g..I put R wire to Rh/Rc jumped, Y to Y, G to G Hmmmm where does the black wire, which is twinned with another black wire and attached to the C terminal at the furnace go? I tried a few things and got the AC going with furnace fan going by putting the Black wire with the G wire at the thermostat, but now the heat doesnt work. Can you or someone help me out? Ive bought quite a few tstats but none have a B (black) terminal. Thanks.

[@vkhubani]

I don't have a C connection at my furnace... i have a T... is that the same thing?

[@Homehandyman101]

@americanflo773 I would check down at the furnace level to see if the G wire is connected properly.

[@kevinsiles88]

my furnice shows a "c" connection and no "g" but when I try to to put the "the "C"connection on the "C" terminal on the thermostat the fan doesn't turn on. what do I do?

[@hdtube99]

Thanks for the video that's what I was looking for. So, now when A/C (Y) is on, the fan is on, because Y and G terminals are connected. But what about the heating? The fan will no longer turn on when furnace is turned on. How do you solve this problem?

[@LordDirus007]

With this configuration do you lose the ability to run the fan separately?

[@lakersfankb2486]

yup

[@adamvandemark1798]

James Charbonneau Yes you would. The G terminal is what powers your fan relay. If you do run your fan in the "on" position this wouldn't be something you would want to do.

[@ratboypest]

this is as good a place as any to ask... i have an oil furnace that is relatively new the model is OHB5-F059-085-3. it has c-y-g-r-w-p from top to bottom on the furnace connections panel. i have no ac, no heat pump, nothing other than the furnace. i have a two wire old thermostat upstairs, that i replaced with a new honeywell simple digital device. there are no buried wires in the wall, it was originally a two wire run when the old oil furnace was installed in 1947. the new thermostat has a fan only switch, which says fan- and 'auto' and 'on' for options. what i want to do, if possible, is be able to run the fan from the thermostat as fan only. currently, we have to go to the basement and flip the fan switch on the top of the control box on the furnace to do this. it would be difficult to run new wire, so my options were to get a wireless thermostat ($$) or perhaps an add-a-wire type of device? anyone know if i can or cannot proceed with keeping the current thermostat by doing a wiring trick? forgot to mention the current two wires to the thermostat are connected to the R and W terminals.

[@TheCaioKyleBraga]

ok. Did exactly as you showed. The thermostat went on but the system didn't

[@Homehandyman101]

Do you have a gas furnace? If not this solution will not work for you. The reason is that most electric heating systems require the thermostat to control the fan in heat. If you do have a gas furnace with AC make sure you put the jumper in between G and Y at the furnace.

[@Googletubenah]

So the reason to do this is the lack of wires correct . If you had an unused wire you could just attatch it to common on both ends yes???

[@justinnanu4338]

Yes.. If you have a 5th unused wire just connect the same colour to the C on both your furnace and thermostat.

[@kef103]

Justin so here's the strange thing . Works fine without the c wire attached . Soon as u add c wire I get error on my nest saying no power at rc

[@theflow03]

Will this trick work if I have a central air conditioning?

[@famoso1418]

did you get an answer for the c wire on the central ac

[@curiosity2314]

This video is great but it lacks in that it does not give voltages on any of the wires. What voltage should the "C" wire provide to the thermostat? Wherever I look the "C" wire is common and normally "Ground" ? What voltage if any is "C" wire?

[@dougiefresh730]

Should be 20-30 VAC. There are no "ground wires" in thermostat wiring. They are all there to complete circuits.

[@seetheshells1976]

What if I don't have a "C" connection on my 20 yr old furnace? I only have W, G, & R. Plus Y all to the t-stat. There are a couple extra wires in the bundle I can use.

[@lakersfankb2486]

the "c" is the common leg off the secondary side (24 volt side) of the transformer. in this case if you dont have c terminal. then you have to wire nut the green wire directly to common wire coming directly off of the transformer. if you don't know what your doing, i wouldn't mess with it

[@LSmiata]

Hello Homehandyman101, I have a heat only application, old two wire thermostat (R and W) Cable has 3 leads between furnace and thermostat: R, W, and "not used"...believe it is a "G" Can I use "G" and wire to "C" on furnace w/o using any jumpers and make my new Honeywell digital wifi unit work correctly? Please advise and thank you for your video. Mr. P

[@LSmiata]

Please cancel all above request. Stripped back cable at thermostat and had 4-wires. At furnace also had 4-wires. All colors match and I apologize for the waste of time. Furnace: I have G and "B/C" (aka B wire for my app) Cheers, Mr. P

[@Homehandyman101]

If you have a conventional furnace, the G wire is the fan and it goes in the G terminal. The Y wire is for a/c and it goes in the Y terminal. If you have one R wire it controls the calling for heat and cool and goes in the RH terminal. The W wire is for the furnace and goes in the W terminal. The black, which is attached to C at the furnace, should go in the C terminal on the thermostat. If you are still having trouble: 877-602-5028 (tech support).

[@klyons20]

the fan will not turn on unless you turn on ac.. if you have the jumper on from y to G

[@TONE_STAR]

Would really appreciate it if someone can helped me out. I too have a com 24v on my terminal block, didn't read anything that would answer my question yet on here or at least I didn't understand it correctly. What to do with a G -com- w- r on terminal? thanks oh and I also have a wire running from the 24v com to the ground...............

[@Homehandyman101]

@gixxtrixx Only G and Y should be jumpered, and only if it's not an electric furnace. In furnaces run by fossil fuels, you can jumper the G and the Y on furnace level, but do not jumper the G and the W.

[@Homehandyman101]

You only use this if you have a gas furnace and you don't have enough wires going to the thermostat to have a C wire. Note not all thermostats require a C wire. I don't believe it will help with your no heat issue. -- To test it see if it is a furnace or tstat problem you would need to do a wire test. To tell you how to do that I would need to know how the thermostat is wired.

[@ryandunbar1314]

Also I did swap the "green" in my case G wire for C behind thermo

[@TheJustinamazing]

okay but why is there 3 wires connected to the c place in your furnace

[@adamvandemark1798]

TheJustinamazing in a hvac system there can be very many points of common. His just so worked out that he has multiple wires on his terminal block. Do not pay attention to this when you are wiring yours. You may have 7 on yours etc

[@klyons20]

fan is automatic in heat mode.. the jumper is to run fan during ac mode.

[@eldoradoboy]

or you just use the Venstar add-a-wire which will allow you full fan control, heating, and cooling when only 3 wires exist at the thermostat

[@Homehandyman101]

Glad to here it was of help

[@milfersy]

you right this guy its doing on his unity but every furnace is diferent and also you dont realy need to have a C conection on your t stat just use a t stat with batery

[@dougiefresh730]

Wifi thermostats dont use batteries. That's why you need a Common to power the thermostat.

[@SyCoREAPER]

@@dougiefresh730 That is entirely false. Emerson Sensi ST55 can run entirely on batteries alone. !one has been using the same batteries for close to 2 years without a C-Wire or hack.

[@dougiefresh730]

@@SyCoREAPER Weird I just went to their website and it tells me I DO need a c wire. Find out for yourself here manager.sensicomfort.com/redirectpages/wirepicker/wire-picker.html.

[@el_teeny]

sorry, why do we jump y to g? thank u.

[@adamvandemark1798]

David R. Jumping your Y to the G terminal gives your G terminal 24v when you get a call for cooling. During a call for cooling you get 24v to the Y wire and 24v to the green wire. Since we are robbing the G to use as a C we don't have to remember to change the batteries every 6 months. This will give your thermostat 24V coming in and a common for it to go back to on your transformer. What this basically does is when you get a call for cooling it acts like a G wire in this situation. Your system will see 24v where it needs to if wired correctly like the gentleman showed in the video.

[@mohammedmouilah7390]

What is I dont have a C in the furnace terminal?

[@Homehandyman101]

So we understand you correctly, your furnace has no G terminal. Is your furnace a conventional furnace of a heat pump? This method of adding a C wire will not work with a Heat Pump and it will not work if you do not have a G wire. You may have to purchase a plug in transformer which is a topic in another of our videos here on Homehandyman101.

[@milfersy]

look for B conection on furnace o check after the transformer there is a C and 24 volts

[@janizary-8767]

0:54 Windows Paint?

[@stevecoscia123]

Sorry, they wont have any fan control on the thermostat. They may use that function for filtration.

[@Homehandyman101]

The clicking noise means the thermostat is working properly. The wiring seems to be the problem. Remember that this method does not work with heat pump systems. Check the wiring at the furnace: there are often several wires on the C terminal - make sure they all make good contact. Call the friendly folks at tech support and tell them which wires you have. They can troubleshoot the wiring for you: 1-877-602-5028

[@stevecoscia123]

Problem:: if customer puts fan on with stat. Condenser will come on also!! Not good.

[@klyons20]

fan run auto in heat mode and jumper if for ac mode.

[@Carskinify]

Why are the manufacturers so obsessed with the fan switch? I wish they would omit the damn switch. Often when I go to one of my apts the tenants have the fan on because they think it has to be on.

[@seanconrad4592]

I followed these instructions and thought everything was great until I noticed a few days later that my condenser now runs non-stop. What am I missing?

[@adamvandemark1798]

Sean Conrad Did you wire the R terminal to the Y terminal?

[@SPARKY11900]

If you do whats instructed here , you won`t have independent control of the fan from the T- stat

[@klyons20]

fan work in auto when using heat no need to jumper

[@OregonDARRYL]

C- common, Y-AC, W-Heat, G-fan. Red-hot 24v.

[@thetruth7839]

Just spent $20 on a Honeywell t h p- c wire adapter and I could have just did this

[@fishermechanical3715]

There is no reason to do this when there is an "add a wire" on the market and you maintain all control.

[@MrTws1220]

That's what I experienced also

[@americanflo773]

THE FAN WILL NOT WORK ON MANUAL MODE...!!!

[@ochoball08]

learn some new. thanks

[@myrouterwentoffline3288]

Using your G wire as your C wire is a TERRIBLE idea!! I added a Honeywell RTH6580WF to my home recently. I discovered no c wire. Without knowing what all it involved, I found the blue wire tucked into the wire bundle as it had been cut off since not in use. I stripped it and applied it to my thermostat. Still no power. I then went down to my furnace to see the blue wire was not hooked up either it was just wrapped around the same wire bundle going to the thermostat. I stripped it and hooked it to the C terminal on the furnace. Now the C terminal had a white and brown already attached going to the AC. But you can hook more wires to the C. You can hook the 3 right into the terminal or you can bundle them together with a 4 wire called a pigtail then you only have one single wire hooked to the C terminal. User preference. So don't just assume because you found the blue wire in your wall or wire bundle behind your thermostat that its connected to the C terminal in your furnace. You will be best to take the panel off your furnace , find if a C wire is connected and determine the color while making sure it's the wire bundle going to the thermostat.

[@theflow03]

Will this trick work if I have a central air conditioning?

[@el_teeny]

can i do this if i have no y wire coming out the wall by thermostat and have a central air unit?

[@adamvandemark1798]

David R. Do you have a blue wire connected to your Y terminal? Chances are you have 18/5 running to your thermostat if so. I would suggest pulling the wire out of the wall a little to check. You probably have a Y wire that is not in use.