air pressure switch problem i think but any advise would be greatful. When both air tube (red/white) are connected to air pressure switch combi will not fire dhw or heating. Red tube runs to top of boiler and draws air through to switch when fan come on, white tube connected to small hose connector which is vented through to inner casing of combi. If i disconnect the white tube which vents into the inner casing the combi fires instantly with fan running all ok. Heating also firing ok. Any ideas of the problem all tubes clean and free from splits etc.

Stu, June 2008

My red air pressure tube is disconnected! The heating always fires up ok and goes off on the timer as it should! But after very big gas bills i inspected the boiler to find this red tube was not connected? and then realised after listening carefully the whole thing shuts down every 2 mins turning the pilot out the fan off and everything. Then a few seconds later it all fires up ok for another 2-3 mins? Surely thats not normal to be doing that for 3 hours whilst we have the heating on? Does it take more energy to fire it up than to keep it running continuous????? Is this shutting down on a glow worm 44ff fan boiler normal?????? And whats going to happen if this red tube is'nt fitted??????? Cause after all the heating and hot water does work ok!

kerry, March 2009

check the venturi that the tubes connect to (inside the flue) it may be partially blocked, mis-shapen from heat exposure, or damaged. Also check that your flue is 100% unblocked (also at terminal for over growth etc.) check all flue seals are in good condition.

If the boiler fires, aps is working ok usually.

T, June 2008