We have a Worcester Bosch Greenstar 25si (mk iv) combi boiler which has developed a problem - I think!
Central heating aspect is fine, boiler pressure at recommended level and so on.
Last week, we noticed that, when having a shower, instead of a constant flow of even-temperature water, the shower was producing hot water, then cooling slightly, then getting hot again, then cooling slightly - constantly over the period of the shower.
The 'boiler lit' light stays on when water is running - although I think the 'burning' sound is switching off - so I think it's switching itself on and off.
There are no flashing 'FAULT' lights or indicators on the boiler - all seems fine.
Our shower is just a wall mounted mixer tap over a bath - nothing fancy, one control lever, pull out for on/off and turn left or right for hot/cold -cost about £20 and has worked fine for last year.
I've tried to test the water temperature variation in the bath and kitchen sink and I 'think' it's doing the same at these taps.
I've turned the water temperature UP and DOWN at the boiler and it makes no discernible difference to the problem - but does make water hotter and colder.
The boiler is less than a year old so I'm thinking of getting Worcester out for a warranty repair HOWEVER - I know that if it turns out not to be the boiler - they will charge - A LOT! - so I'm trying to eliminate all other possibilities before calling them.
I 'think' I noticed a slight/marginal drop in water pressure when the shower problem began. I've been running cold water to check - the pressure still seems high but maybe slightly lower than it was before the problem began - not lower enough for me to remark upon it independently of the shower problem - it's probably gone from 'blast your face off' high pressure to 'splashes on the front of your shirt if you're not careful' - so probably a fair bit of a drop.
After this long tale of woe - would the drop in water pressure cause the boiler to switch on and off during a water heating cycle (if so, can this be remedied?) OR is it more likely to be an internal/mechanical problem with the boiler?
The weather here has been colder but not freezing and didn't cause the boiler any problems last year (colder) so I don't think it's that.
I've googled this and there are other people out there with the same problem - but I can't see where anybody has found a solution - nobody posts the solutions - buggers!