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.