Worcester Bosch NTC Sensor Max 87186854830

The Worcester Bosch 87186854830 is an NTC sensor — a negative temperature coefficient thermistor — used across the Greenstar family of gas boilers. It sits in the water circuit and reports temperature back to the appliance control board, which uses that signal to regulate heating and domestic hot water delivery. A drifting or failed sensor gives the board false information, so the boiler can run outside its intended temperature range or refuse to fire.

• The boiler locks out or fails to fire, with a temperature-related fault code shown on the display.
• Domestic hot water temperature swings between hot and cold instead of holding steady.
• The heating circuit runs noticeably hotter or cooler than the set point on the thermostat.
• The boiler short-cycles, firing and shutting down repeatedly over short intervals.
• A multimeter resistance check on the sensor reads outside the expected range for the water temperature at the time of testing.

• Check the GC number on the appliance data badge against the compatibility list to confirm the sensor suits your model.
• Compare the part number on the sensor being removed with 87186854830, and with the earlier numbers 8-718-602-09A-0 and 871860209A0, which identify the same item.
• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.