NEST 3rd Gen heat won't come on but fan does

[Kennystewart80]

Hey, My furnace comes on but won’t ignite a flame, so just blows cold air. Hooked up my old thermostat again and it worked just fine. Any thoughts from anyone ?

Also, this is my second time posing this as I had email issues. Some people did reply to my first post and I appreciate you guys, I'm locked out of that thread now but would love it if you could help again lol, promise you won't be ignored this time. I honestly thought nobody replied.

[Houptee]

Is it programmed correctly for the type of system you have? Maybe go thru the setup all over again make sure you say it is a hot air heat system.

Next step if that is all correct requires a multimeter.

W wire should get 24v AC power when Nest is calling for the furnace to turn on the heat.

Only way to test is put Nest back on and turn on heat, then go to the furnace and use a meter set on AC volts and test for 24V between W and C at the furnace.

If no power found on W then something is wrong with the Nest.

[Kennystewart80]

I don’t have a C wire, so I’ve ordered the power adapter they advertise as the alternative to a C wire. Friend of mine had issues too he had a C wire installed and it was perfect. 

tbh tho, I don’t feel like it’s a C wire issue as  the nest calls for heat, the fan starts but just blows cold air. No ignition. The power thing arrives Friday so soon find out I guess lol. 

[Houptee]

Most furnaces the fan will not start until the unit fires up reaches temp then fan starts running.

In AC mode the fan starts right away.

So if you can post pics of old wiring and the nest wiring we might be able to help you.

[Jhonleanmel]

Hey folks, 

Thanks again for helping here, @Houptee. 
@Kennystewart80, I hope you've got the answer you're looking for. If you're still in need of any assistance, feel free to let us know. 

Best,
Mel

[Kennystewart80]

No AC, live northern Canada lol. Furnace cycles on, just blows cold air out the ducts for approx minute then shuts off. Reconnect old thermostat works perfect. 

[EdwardT]

Hi Kennystewart80,

Thanks for the response. I'd love to know more about this and I have a few questions:

• What type of Nest Thermostat do you have?
• How is your Nest Thermostat wired?
• What is the power reading of your Nest Thermostat?

Looking forward to your response.

Thanks,

Edward

[Kennystewart80 · Accepted solution]

Hey all,

Thanks for the hints and tips, I bought the power adapter thing and it all works perfect now. 

cheers. 

[EmersonB]

Hey everyone,

@Kennystewart80 awesome — glad to hear that and thanks for getting back to us. We'll then go ahead and lock this thread after a day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.

@Houptee, @mel and @Edward I appreciate your help.

Regards,
Emerson

[EdwardT]

Hi ennystewart80,

I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.

Thanks,

Edward

[EdwardT]

Hi Kennystewart80,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Thanks,

Edward