A red thermostat indicator does not by itself prove that the thermostat needs replacement.
Record the thermostat model and any displayed message before diagnosing a red light. Indicators differ between generations, so do not replace a thermostat solely because a red light is visible.
For an nJoy UWG5-4999, a flashing red light on the side with GFCI TRIPPED PRESS TO RESET indicates a tripped GFCI. This occurs during the deliberate monthly GFCI test as well as after a ground fault.
After the monthly test, press the side reset button briefly. A check mark confirms a successful reset. If the reset fails, the message returns, or the GFCI has tripped because of a fault, have the installation inspected. Do not bypass the GFCI.
For a different thermostat, use that model’s manual or contact WarmlyYours Technical Support at (800) 875-5285.
Sources
- Manufacturer instructions (publication 13031), PDF pp. 32–35.