Noritz Control Signal / Thermostat Interface Issue

Boiler's display and controls work, but there is no call for heat from the thermostat.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Open thermostat circuit, Incorrect wiring to Noritz boiler terminals, Faulty external control relay, Broken thermostat cable

How to Fix / Troubleshooting

Safety: Turn OFF power before working on low-voltage control wiring.

  • 1. Verify thermostat settings: Ensure the thermostat is set to HEAT and above room temperature.
  • 2. Check wiring at boiler: Inspect the thermostat or control wires at the Noritz boiler's low-voltage terminals for loose or broken connections.
  • 3. Bypass test (qualified persons only): Momentarily jumper the call-for-heat terminals at the boiler to see if it responds. Remove jumper immediately after test.
  • 4. Professional troubleshooting: If the boiler responds to a jumper but not the thermostat, the thermostat or wiring is likely faulty and should be replaced.
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Repair Difficulty

Medium 3/5

Required Part

Room Thermostat
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