Vaillant Combi boiler - no hot water

[barry999]

Hi. I have a Vaillant combi boiler which is having problems producing hot water. Sometimes we can get hot water to the bath but not to hand basin or the kitchen sink, or vice-versa. Sometimes there will be no hot water at all. When there is hot water, the temperature isn't very high (you can have a bath but can't stay in too long before it becomes cold). I was wondering if this could be fixed or do I need to replace the boiler. The boiler model number is either VCW GB 242 E or VCW GB 282 E (taken from wiring diagram inside door) and is just over twenty years old. The CH works fine.
Thanks

[htg engineer]

Do you find it's worse at peak times? in the morning and tea time when the water usage in the street will be higher? if yes then you need a diverter service kit, over time the diaphragm becomes stretched and may split. It's also a good idea to replace the fulcrum arm too as they do snap.

htg

[barry999]

No, the problem happens anytime