gas stove wont shut off

[rreale]

My Napoleon | GVFS20 Arlington wont shut the main burner down when it reaches the temperature set on the thermostat. the stove is connected to a battery operated thermostat, just uses a red and white wire. i tried another thermostat, same issue. it worked fine for 13 years

I havent cleaned the thermopile in a few years, could that be the problem?
The pilot functions fine.

 

[DAKSY]

Have you pulled the wires from the back of the thermostat & jumped them?
Does the unit turn on & off when jumped then separated?

 

[rreale]

yes i have tried it and it has no effect. when i remove the thermopile wires, it shuts off.
When i test the resistance across the TP and TH terminals i get a 0 reading. i am starting to think it could be the valve.