Err 15
Burnham Gas Valve Modulation or Communication Fault

Boiler shows “Err 15” and will not modulate, stuck at low or high fire

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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

Failed modulating gas valve actuator, Broken communication harness between valve and control, Incorrect gas valve calibration, Control board output failure

How to Fix / Troubleshooting

Safety first: Turn off power and gas. Gas valve work should generally be done by a licensed technician.

  • Inspect harness: Locate the multi-wire harness between the control board and the modulating gas valve. Ensure connectors are fully seated and wires are not damaged.
  • Check for kinks or strain: Make sure the harness is not pulled tight or pinched by the boiler cover.
  • Reset control: Restore power and reset the boiler. Observe if the boiler now modulates normally or if Err 15 returns.
  • Professional calibration: If the error persists, a technician must verify gas pressures and may need to replace and calibrate the gas valve using manufacturer procedures.
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Repair Difficulty

Professional Required 5/5

Required Part

Modulating Gas Valve
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