Vaillant 242e Hot Water

ifti

i have a gas safe engineer coming out tomorrow to take a look at my boiler but I just need advice just in case they end up replacing parts that are fine.

the problem is as follows :

when I open my hot water tap the pump starts then all of a sudden cuts off.

then after a few seconds it starts up as normal and stays on.

then about 10mins later it cuts off for a little while and then starts up again.

we recently had a diverter value replaced it only lasted 13 months so im worried they may just change the diverter value again. im hoping I can keep a eye on him this time and makes sure he only changes the part that needs to be changed and not 3 different ones.

any help would be appreciated.

thanks in advance.