pressure drop in my boiler

[goosey]

hi chaps, got a fault with my worcester 350 boiler. hot water works fine and heating switches on straight away, but after i have switched the heating off the pressure seems to drop and only when the system is recharged will it switch on as low pressure light illuminated.

 

[goosey]

could it be as simple as the pressure relief valve?? will check it out in the morning. thankyou.

 

[goosey]

mine was also a question, i will check it out in the morning and go from there thanks for you help.