Our gas logs will only come on when turned to the on position. When turned to the auto position, which is supposed to engage the thermostat, they do nothing. The thermostat has no battery as it used a thermocouple. Any suggestions?

Make sure the thermostat works with milivoltage systems

Make sure the thermostat works with milivoltage systems

I know it does because it used to work fine.

Remove thermostat and attach the two wires together. This will eliminate the thermostat as the possible problem.