the primary thermistor is located on the right hand side of the heat exchanger as you look at the boiler remove the front casing then the front combustion plate then the rhs plate as you look at the boiler you will see the thermistor drain down the boiler and remove the thermistor using a 13mm spanner and reassemble in the reverse order be careful to fit the metal washer good luck
ricky
March 2008
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