My combi boiler is playing up a little bit recently. Wondering if there is anything I can check and fix before calling in a professional?

The problem I’m having is first time you turn the hot water tap on the boiler fires up fine and heats the water up fine. But after a while the boiler turns the flame off. It only retriggers the flame if you turn the tap fully open. Normally it will trigger the flame after only opening the tap a little bit.

Many problem seems to be the shower which doesn’t have a high enough flow rate to trigger the boiler again. Other taps in the flat have enough flow rate to trigger but not the shower.

Is there anything I can check on the boiler and fix my self or will I have to call in a professional? Also realised the boiler hasn’t been serviced for 16 months. Is this something that could be fixed with just a normal service?

Is it making any grinding or whining noises? Could be the fan sticking.

I don’t think it’s making any more noise than normal, but will check again when home.

Same a while ago it was the fan on ours.

Diaphragm.

Pressure?

check you haven’t got a pressure regulator in the system.
If there is it needs to show 3bar when the tap FURTHEST away from the reg is open fully (usually a shower).
I’ve had this happen and do exactly the same thing. Plays havoc with the thermostat in the shower too.