I have a Glow-worm 38cxi combi boiler. Just recently the hot water runs just warm even if it is turned to maximum. Also the upstairs radiators come on when i run the bath. The boiler is only 3 years old.

Ken, May 2009

This diagram...

http://www.diyfaq.org.uk/plumbing/combi.html

shows the paths for hot water and heating - if the diverter valve is in the wrong position (stuck half way) the heat output might be shared between rads & taps even though it should all go to the taps.

I would suspect the diverter valve being defective and causing your problem.

Peccavi, May 2009