hi mary,the error indicates a faulty DHW sensor.it is located behind the gas valve and has two red wires connected to it.it can be removed with a 13mm spanner.this sensor can be changed WET or by draining the c/h system.it can be changed without removing the gas valve although its a little tricky.if you are going to change the sensor WET,not draining the system,you must first isolate power to the boiler,have ready the new sensor and gasket the threads on the sensor blued up,that's just a blue gasket sealer..and swiftly remove old and fit new.I say swiftly because you will get a flow of water on removal .if for any reason you cannot get to the sensor with your spanner don't be tempted to remove the gas valve.this job is for a gas safe engineer.the part no for the sensor #8484.hope this info helps.
ozone, December 2011
