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Mend Alpha CB24 Heating Hot Water Boiler

Alpha CB24 Flashing Indicator Neons, No Hot Water/Heating, please help?

On sunday I discovered my Alpha CB24 had no power. On inspection, the main terminal fuse had blown. With a bit of trial and error I found that disconnecting the fan from the circuit board and replacing the fuse powered the boiler back up. So I replaced the fan yesterday (Monday). Everything worked fine for a night and day, done the dishes this evening and we had hot water. Then 10 mins later go to run my daughters bath and theres no hot water. When you turn on the heating or run a hot tap the boiler makes a noise like its trying to do something and then the yellow and red indicator neons start flashing together.
Please can anybody help?
Thanks

David
May 2012

Alpha Alpha CB24 Heating, Home Heating Systems Heating Hot Water Boiler

alpha cb24
47-532-15
you say you have replaced the fan
was the replacement part number 1.017264?
installation manual
page 18
section 6.5
red & yellow neon lights flashing TOGETHER
blocked flue or fan fault
assuming flue is ok there are basically 3 components that could be causing problem
FAN [unlikely as it has already been replaced]
PCB
APS air pressure switch
if you're handy with a multimeter its possible to find the faulty component
FAN runs on 240 volts AC & fan coil has internal resistance of 35 ohms [cold]
APS runs on 24 volts DC
if this information doesnt make sense to you then you have no option but to get a competant gas engineer to fix boiler for you
APS 1.8396 £60
PCB 1.017118 £200

manwithnoname
May 2012