Nest thermostat won't consistently ignite gas furnace

[tttmmmhhh]

I have a gas heater that works fine on older thermostat. W, RH and G wires. Very simple set up. 

Installed Nest because I had one in previous home and loved it. Problem is that in new home Nest installation the furnace will about half the time try to ignite (I can hear it making noises) but it will just turn off again for a few seconds and then try again. It will continue doing this until I turn the thermostat down. Usually, when I try again a few minutes later it will work properly and ignite the furnace fine.  

Sometimes when everything is working fine the furnace will shut down before the thermostat reaches the desired temperature. The Nest continues to show that's its heating, but the furnace is off. 

Both problems seem to be getting worse as days go by (I installed Nest a week ago).

Old thermostat still works fine when I replace the Nest with it, so it looks like the problem is with the Nest. Checked and double-checked the wiring and it's all done according to instructions.

Help!

[CoolingWizard]

@tttmmmhhh , What you are describing appears to be two different symptoms that might not be related. We need to evaluate the basic troubleshooting steps. First make sure the conductor wires are fully inserted. The Nest thermostat is a learning thermostat and such it does need time to learn the performance of your system. What model of thermostat did you purchase?  

AC Cooling Wizard

[tttmmmhhh]

Thanks for the reply. I have the learning thermostat 3rd gen. I am certain the wires were fully inserted. I have owned the same model in a previous home and I’m familiar with how it’s supposed to work.  I think there may be something wrong with the thermostat. Will resetting if and reinstalling be helpful?

[CoolingWizard · Accepted solution]

@tttmmmhhh , if you’re using a nest learning thermostat, then you are either using a power adapter or you are using the alternative common wire access using the W wire. Because you did not list a C wire as being present In your system set up., Is your thermostat remaining full fully charged?  The key is to ensure your heating system uses a 24VAC a power source.  Can you get me the make and model number if your furnace? 

AC Cooling Wizard