Ideal Thermostat Sensor Harness Classic 137658

The Ideal Thermostat Sensor & Harness Classic is a temperature-sensing assembly used on Ideal Classic FF and Classic FF LX boilers. The sensor reads boiler temperature and feeds that signal back to the control circuit, which modulates firing to hold the appliance at its set point. It is supplied as a sensor with its wiring harness attached, so the connection back to the control board is made in one piece.

• The boiler runs but does not reach or hold its set temperature, or cycles on and off more often than usual.
• Heating or hot water output is erratic, with the appliance cutting out before the system is up to temperature.
• The boiler locks out or shuts down shortly after firing, with a temperature-related fault indicated.
• The sensor probe or its harness shows heat damage, brittle insulation, chafing or a broken conductor at the plug.
• Temperature readings at the boiler disagree with the actual flow and return temperatures measured on the pipework.

• Check the GC number on the appliance data badge against the compatibility list, as the same boiler range was built in several variants.
• Note the alternative number 1176560 when cross-referencing against older documentation or stock records.
• Inspect the sensor pocket and any sealing washer at the same time, as these are disturbed when the probe is removed.