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Furnace not lighting

Gmdh2o
Community Member

I just installed a Nest Smart thermostat. It replaced a dumb (no timer, just temperature and manual switch between AC , heat, and fan) digital unit. 
I wired in Y, W, G, R from the old unit. Found the C wire and connected that. Not used for the dummy. 
Nest wiring checker indicates it is compatible. There was a jumper between R and Rc but Nest says to not use it. 
the Nest appears to work and fires up the fan when the set point is above current temperature. However, the burners do not ignite. 
the furnace is fine. When I put the old unit back everything works? 
Is there anything I can do fix this? Or am I stuck in the Middle Ages? 
thanks. 

13 REPLIES 13

Patrick_Caezza
Diamond Product Expert
Diamond Product Expert

@Gmdh2o 

Post a picture of the original thermostat's wiring.

Are you sure that you have the Nest Thermostat E as it is only available through a Nest Pro. Could you have the Google Nest Thermostat (2020) which has a mirrored display?


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@Patrick_Caezza 

Hi, it is the Smart Thermostat not the ‘E.’  I don’t know what the ‘E’ is, which makes sense if it is for pros only. I don’t see an option for posting images. 

Gmdh2o
Community Member

@Patrick_Caezza 

Yes, I believe your description matches my device. It is slimmer than the Learning model I had previously, and does have a mirrored screen. 

Patrick_Caezza
Diamond Product Expert
Diamond Product Expert

@Gmdh2o 

You can post pictures by doing this.

Camera icon.jpg


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@Patrick_Caezza  I don’t have that button. My toolbar has only five options in fact. Maybe an iOS limitation? I can take a look on an Android device in a few days when I get back from a trip. 

Patrick_Caezza
Diamond Product Expert
Diamond Product Expert

@Gmdh2o 

 

No worries, it just means you community account is new. 

You can use any online storage like Google drive and then sharing a link to the picture here.


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@Patrick_Caezza @Here you go. Old and new. 
Original wiring 

Nest wiring 

Gmdh2o
Community Member

@Patrick_Caezza  Any thoughts after seeing the photos? I’m hoping to get it set up this week before heading out on a trip. Thanks. 

Patrick_Caezza
Diamond Product Expert
Diamond Product Expert

@Gmdh2o 

Sorry, things have been a little hectic around here.

Your wiring looks correct. Did you check the furnace end of the blue wire and ensured it is connected to the C terminal there?

Swap the white (W) wire and the yellow (Y) wire and then call for cooling. Do the burners ignite now? 

If they still don't, take the White, Green, and Red wires. Connect them together and see if it works. If it does, then it looks like you have a bad Nest.

 


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@Patrick_Caezza  No worries, I really appreciate the help. This is what I see at the furnace end. It seems the blue wire is not connected. That matches what was the case at the thermostat end. 
https://drive.google.com/file/d/1D8wjU6NOlgndK509bHOI6XtI49OsM2U3/view?usp=drivesdk 

Patrick_Caezza
Diamond Product Expert
Diamond Product Expert

@Gmdh2o 

If the blue wire isn't connected to the furnace then you do not want it connected to the thermostat.

Can you post a picture of the make and model number of the furnace? There should be a large label on the cover with that information.

Did you try either of the troubleshooting steps?


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@Patrick_Caezza Not tried anything yet, just got back home. Will try in a minute to swap those two wires. In the Nest I assume. 

Here is the model sticker. Sticker 

Gmdh2o
Community Member

@Patrick_Caezzaswapping white and yellow at the Nest does indeed trigger the burners when calling for cooling. Also for heat. Burners on either way. 
I noticed the device thinks the heating is electric and won’t let me select gas. Don’t know if that matters.