Worcester 24i junior?

hi..

i have recently had problems with my worcester 24i junior...the pressure went from it..so i had no hot water. i had help finally and turned the tap to let the pressure back in (it now sits at 1 1/2), now the boiler starts up for 10-15 seconds then the red warning light flashes and soon afterwards the boiler stops. still no hot water, please help.

dan