On the covered Sensi smart thermostat, Call for Service with a wire in the L terminal means if there is voltage on the L wire, the diagnostic terminal, Sensi says the thermostat displays Call for Service. Sensi is explicit that the L wire is not needed for normal thermostat operation, which is why disconnecting it is the first troubleshooting step rather than a workaround: nothing the thermostat controls depends on that terminal carrying a signal. First, look for a wire in the thermostat's L terminal.
Try in this order
0 of 2 completedWhat to do first
ReversibleLook for a wire in the thermostat's L terminal.
Correct only the documented fault domain
ReversibleSensi's step: remove the wire from the L terminal, push it back into the wall and reinstall the thermostat to see whether the message goes away. If that resolves it, Sensi says you may want a service professional to find out why there is voltage on the diagnostic wire, but if the system operates as expected leaving it off is a personal preference. An L terminal on a furnace control board is commonly used to signal a lockout or fault condition back to the thermostat, which is one reason a technician who wires it up deliberately, rather than a stray connection, might want to know it is carrying voltage before it gets disconnected for good.
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What does Call for Service with a wire in the L terminal mean on a Sensi smart thermostat?+
If there is voltage on the L wire, the diagnostic terminal, Sensi says the thermostat displays Call for Service. Sensi is explicit that the L wire is not needed for normal thermostat operation, which is why disconnecting it is the first troubleshooting step rather than a workaround: nothing the thermostat controls depends on that terminal carrying a signal.