hi iv'e got no hot water the c/h works fine when you open the hot tap & put a demand on the boiler the pin isn't coming out to close the switch . so ive replaced the diverter valve & still the same. any ideas ?

darren jones, September 2008

try replacing the diaphragm in the pressure differential assembly. they perish and let water in on both sides of the d/phragm, also the pin sometimes sticks with scale. isolate the cold inlet to the boiler (second black tap lever from the right) on the jig and open a hot tap to release some pressure. the front of the pressure diff is held by screws around the outside edge, undo these and put the new diaphragm in (clean the pin aswell)

notsayin, September 2008

sorted fault thank you very much.that'll teach me to buy a second hand boiler with no book ! i'd piped the hot &cold wrong way round. but now & then was getin hot water for a few seconds so though nothing wrong with piping..wonce again many thanks . on the plus side i feel i know my boiler intermetly now. lol

darren, September 2008

Hi Darren,

if you have just fitted the boiler check that the cold in and hot out pipes are the correct way round. If it has been installed a while and worked ok then the only problems can be, small pipes to diaphragm unit blocked or on the wrong way round, or the pressure differential unit on the other end of the small pipes faulty.

Ian, September 2008

did you change the assembly complete with front water section or did you use your old water section?

have you changed dhw diaphragm and checked sensing pipes are clear

iain, September 2008

yes ive changed the complete diverter assembly

darren, September 2008

you've changed full divertor assembly??????? have you changed the dhw diaphragm in the front brass section behind microswitch?

iain, September 2008