HVAC heat won't stay on.

[mitcheda01]

Hi ,

I installed a nest thermostat this last summer and now that colder temps have set in, I've changed it over to the heating mode. The HVAC heat will stay on momentarily and then switches off. I sometimes also hear the gas starting up but then also powers down while the blower stays on momentarily. Here's the wiring I currently have....

Green to g. Red to R. yellow to y. Blue to c. White to w

[Patrick_Caezza]

@mitcheda01 

If you have it, can you post a picture of the original thermostat's wiring?

[mitcheda01]

Issue fixed! Thank you!

[Azaghan]

How did you resolve? I have this issue also. I had my nest working for AC but it wont work for heat. Nest would not light the auto-pilot. I had to switch back to my old thermostat (Sensi).

EDIT:

@Patrick_Caezza

I have a pic of current Sensi thermostat, but I do not see a way to upload it. I currently do not have access to google drive at this time to generate a link.

[Patrick_Caezza]

@Azaghan 

Click on the little camera icon that is in the Relying to box

[Azaghan]

@Patrick_Caezza

Originally on the nest (above) I had the Y in Y1 and the WHITE in W1. This picture was after attempting to get heat to kick on.

This setup with the sensi thermostat works for both AC and HEAT.

Just to clarify, I use an external power source.

[Patrick_Caezza]

@Azaghan 

You have the wiring mixed up.

Green - G to G

White - W/E to W1

Yellow - Y to Y1 (2nd stage cooling)

Blue - Y2/* to Y2

White - C to C

Red - RC to Rc

White - RH to Rh

[Azaghan]

@Patrick_Caezza 

Thank you for your assistance. The heat in deed did come on. However, now it won't shutoff. Even with thermostat disconnected, I had to go shut off furnace manually. Upon turning the furnace back on, the heat still came on with out the thermostat.

I unhooked Y, W, and rc. Still had to manually turn off furnace.

Any advice?

[Azaghan]

@Patrick_Caezza 

My apologies, I mixed up the wires again. Ugh. Followed your instructions and now I am working as intended.

EDIT: The heat still does not work. When I move Rc to RH the heat stays on. Otherwise the auto pilot will not engage when hooked as you described. The AC works just fine however.

Thank you for your help!

[Azaghan]

@Patrick_Caezza 

Still no heat. I have tried all kinds of configurations. Even reset my thermostat to rule out a messed up a setting.

Only config that gets my heat going in the R to RH to keep the heat circuit open.

[Patrick_Caezza]

@Azaghan 

Interesting, have you looked at the wiring in the furnace to make sure it matches the thermostat wiring? Post a picture of it if you can

[Azaghan]

EDIT: (Current Config)

@Patrick_Caezza 

Top

Bottom

Extra

Extra

 I looked at my board at the beginning of summer when I was trying to figure out the AC, but I honestly have no idea what they did.

The other wires I posted pics of are in the wall near my thermostat. However, they were not used in the Sensi thermostat setup. I believe they were used with the original thermostat but that was so long ago I am not certain.

Current Config. AC works, NO Heat

[lusvin]

Hi @Azaghan,

Thank you for posting in the community. I’m sorry to hear that, after all your efforts, the concern persists. Let me help you with this. 

In this case, to solve this situation, my recommendations for you to make the process and the assistance easier and safer for you are to get in contact with a professional to get installation help from a professional.

Let me know if you have any other questions.

Best regards, 

Lusvin.