baxi 105e instant pump and fan wont stop running

[wiggy1962]

IVE GOT A BAXI 105E INSTANT WHICH IS FIVE YEARS OLD WHICH HAS DEVELOPED AN ANNOYING FAULT.THE FAULT OCCURS WHEN HOT WATER IS RUN FOR A WHILE THE THE PUSHROD FOR THE DHW DIFF VALVE IS RIGHT OUT KEEPING THE MICROSWITCH LIVE,WHEN THE TAP IS TURNED OFF THE BURNER RUNS FOR A MINUTE OR SO THEN CUTS OUT,THE PUSHROD HOWEVER STAYS OUT AND KEEPS THE MICROSWITCH LIVE WHICH KEEPS THE FAN AND PUMP RUNNING WHICH KEEPS THE BOILER IN THE HOT WATER MODE.THE ONLY WAY I CAN GET THE HEATING TO WORK IS TO TAKE OFF THE MICROSWITCH OFF AND PHYSICALLY PUSH THE PUSHROD BACK IN AND REPLACE THE MICROSWICH AND THEN THE PUMP AND FAN GO OFF.I HAVE CHECKED PUSHRODS FOR GUNGE ETC AND GREASED THEM AND DIAPHRAM IS OK AND SMALL PIPES ARE CLEAR ,IT SEEMS LIKE TO MUCH PRESSURE ON THE BACK SIDE OF THE DHW DIFF VALVE ANY IDEAS WHAT COULD CAUSE THIS

 

[baxpoti]

It's a pressure differential, try turning off the cold supply tap to the boiler, does this help?

Any taps leaking/dripping or scale on the pres diff pipes?

Remove the press diff and check connection behind, is it leaking,corroded?

Try replacing the press diff unit complete

oh and stop SHOUTING