At times during the day my gas burner doesn't try to come back up to the set temperature on the upstairs or downstairs main thermostat.

I'll hit the up button a couple of degrees but no change. Then when I flip the thermostat switch to off and back on again, the unit fires up for heat maybe 10 minutes or so. Sometimes I have to do that twice for it to stay on but it still doesn't get to the set temp. But at 2am its working again correctly.

I've replaced the batteries on them and swapped the thermostats as well. Sometimes it works for days.

  • 1
    What make and model is your furnace? Can you post photos of its wiring diagram please? Feb 15, 2021 at 4:36
  • 1
    Either the thermostat is faulty or programmed incorrectly or one of the heater's control or safety devices is fault, or is in fact detecting a safety problem with your boiler and shutting it down. You need to triage the problem, eliminating each component one by one. You need at least a simple voltmeter and the circuit schematic for your system. For example, when the boiler shuts down, if you have 24V between W and C at the boiler it means the thermostat still wants heat, so it is not the problem. It could be overheat, low water, etc.
    – jay613
    Mar 17, 2021 at 18:26

1 Answer 1


Three possibilities...

  1. It's a programmable thermostat and it's programmed incorrectly.
  2. The internal clock is set to the wrong time so the programs change at the wrong times.
  3. It's been zapped with static electricity and needs to be replaced.

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