I'm having a problem with my Ariston A23 MFFI Combi Boiler?

I recently fitted a new panel to the combi (it has the main on off switch on it and sends the signal to make it spark).I noticed a wire was off at the pressure switch located at the top of the boiler and has small clear 4 or 5mm hoses on it .I reconnected the wire with a spade connector and thought i had cracked it.When i switch it on i can hear the fan start up but no sparking but on further probing i noticed that when a bridge was made between the two connections i get the spark and it fires up but only for two or three minutes.I created a bridge between these two connections so that when it cuts out i remove one end of the bridge ,listen for the fan ,reconnect and away it goes again for a short time.AAAHH.Whats the problem.