Navien Error Code SH3 Thermostat Status: Input/Output Status item 3 – SH3 Thermostat Status (Boiler)

Updated October 16, 2026 · by Aurora Star Tech Inc.

Navien error code SH3 Thermostat Status on a boiler means: Input/Output Status item 3 - SH3 Thermostat Status. It is also called Navien diagnostic code SH3 Thermostat Status.

Low severityBoilerNavien NHB-H

Homeowner? What Navien code SH3 Thermostat Status means for you

Usually minor Your boiler is reporting: Input/Output Status item 3 - SH3 Thermostat Status. This code is usually informational or minor. The safe checks below often clear it; call us if it keeps showing up.

Safe things you can check yourself

Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
Look at the pressure gauge on the boiler. If it reads much lower than usual or near zero, or water is leaking, call a technician.
Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
Check that the boiler gas valve is open (handle in line with the pipe).
Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.

Call (647) 657-2977 Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does Navien error code SH3 Thermostat Status mean?

Service menu 2. Input/Output Status, item 3: shows the state of the space heating thermostat 3 input. Useful to see whether the control is seeing or sending a signal.

Applies to: NHB-055H, NHB-080H, NHB-110H, NHB-150H

Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

Navien models that use code SH3 Thermostat Status

NHB-055H NHB-080H NHB-110H NHB-150H

Other Navien Boiler codes

Code	Meaning
Outdoor temperature	Outdoor temperature display
Panel F/W Ver	Status Information item 28 - Panel F/W Ver
Return Temp	Status Information item 7 - Return Temp
Service menu	Advanced / service menu (Back + Menu)
SH1 Thermostat Status	Input/Output Status item 1 - SH1 Thermostat Status
SH2 Thermostat Status	Input/Output Status item 2 - SH2 Thermostat Status
SH Operation Time	Service Status Info item 1 - SH Operation Time
SH Set Temp	Status Information item 3 - SH Set Temp
Space heating demand icon	Space heating demand
Space heating temperature	Space heating temperature display
Status Information	Status Information menu
Supply Limit - No. of Times	EMS Data counter 9

All Navien Boiler error codes →

Navien code SH3 Thermostat Status: homeowner questions

What does Navien code SH3 Thermostat Status mean?

Input/Output Status item 3 - SH3 Thermostat Status. Service menu 2. Input/Output Status, item 3: shows the state of the space heating thermostat 3 input. Useful to see whether the control is seeing or sending a signal.

Is it safe to keep using my boiler with code SH3 Thermostat Status?

Usually yes. Code SH3 Thermostat Status is normally minor, but if it keeps coming back have it checked.

Can I reset Navien code SH3 Thermostat Status myself?

You can try one reset (power off for 30 seconds, then on). If Navien code SH3 Thermostat Status comes back, the cause is still there and a licensed technician should check it.

Who can fix Navien code SH3 Thermostat Status near me?

Aurora Star Tech Inc. repairs Navien boilers in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: Boiler Not Heating: What to Check

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Source: Navien NHB-H Installation and Operation Manual, 11.13.2 Viewing Input and Output Status, p.110-111. Written in our own words as a summary; always check the original manual.

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.