How to Fix / Troubleshooting

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

Steps:

Check thermostat type: Ensure the connected room thermostat or controller is compatible with the Intergas boiler (e.g. OpenTherm vs simple on/off).
Inspect wiring: Verify that the control wires are connected to the correct terminals on both the thermostat and the boiler. Look for loose or damaged cables.
Test continuity: With power off, test continuity of the control circuit. Repair any breaks.
Bypass test (technician): Temporarily link the boiler's room thermostat terminals to simulate a call for heat. If the boiler responds, the external control or wiring is at fault.

If communication still fails with known-good wiring and controls, the Intergas communication module or PCB may need replacement.

Code 17 displayed, boiler does not respond to external controls correctly

Possible Causes