Boiler displays E16 and will not respond to the thermostat; the display may show an abnormal room temperature.

Possible Causes

Open or shorted indoor sensor, damaged sensor wiring, incorrect sensor location (heat source influence), faulty control input.

How to Fix / Troubleshooting

Safety first: Turn off power before working on low-voltage wiring.

• Locate indoor sensor: If your Utica boiler uses a remote indoor sensor for reset control, find it on an interior wall away from drafts and heat sources.
• Inspect wiring: Check the two-conductor cable from the sensor to the boiler's low-voltage terminal strip. Tighten any loose connections and repair damaged cable.
• Test sensor: With power off, disconnect the sensor and measure resistance. Compare to Utica's chart for room temperature. Replace if readings are out of range.
• Relocate if needed: If the sensor is near a heat source (sunlight, appliances), relocate it to a more representative location.
• Reset and test: Restore power and verify that the boiler now responds correctly to room temperature.